fix!: drop support for Python 2.7 (#778)

Drop use of 'six' wrapper library.

Drop 'u"' prefixes.

Drop support for app_engine 'classic' mode (Python 2.7-only).

Release-As: 2.0.0b1

Closes #777.

CONTRIBUTING.rst

@@ -18,8 +18,8 @@ A few notes on making changes to ``google-auth-library-python``.
   documentation (in ``docs/``). You can re-generate the reference documentation
   using ``nox -s docgen``.
 
-- The change must work fully on the following CPython versions: 2.7,
-  3.5, 3.6, 3.7, 3.8 across macOS, Linux, and Windows.
+- The change must work fully on the following CPython versions:
+  3.6, 3.7, 3.8, 3.9 across macOS, Linux, and Windows.
 
 - The codebase *must* have 100% test statement coverage after each commit.
   You can test coverage via ``nox -e cover``.

README.rst

@@ -24,11 +24,15 @@ For more information on setting up your Python development environment, please r
 
 Supported Python Versions
 ^^^^^^^^^^^^^^^^^^^^^^^^^
-Python >= 3.5
+Python >= 3.6
 
-Deprecated Python Versions
-^^^^^^^^^^^^^^^^^^^^^^^^^^
-Python == 2.7. Python 2.7 support will be removed on January 1, 2020.
+Unsupported Python Versions
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+- Python == 2.7:  The last version of this library with support for Python 2.7
+  was `google.auth == 1.34.0`.
+
+- Python 3.5:   The last version of this library with support for Python 3.5
+  was `google.auth == 1.23.0`.
 
 Documentation
 -------------

google/auth/_cloud_sdk.py

@@ -18,8 +18,6 @@
 import os
 import subprocess
 
-import six
-
 from google.auth import environment_vars
 from google.auth import exceptions
 
@@ -156,4 +154,4 @@ def get_auth_access_token(account=None):
         new_exc = exceptions.UserAccessTokenError(
             "Failed to obtain access token", caught_exc
         )
-        six.raise_from(new_exc, caught_exc)
+        raise new_exc from caught_exc

google/auth/_credentials_async.py

@@ -18,13 +18,10 @@
 import abc
 import inspect
 
-import six
-
 from google.auth import credentials
 
 
-@six.add_metaclass(abc.ABCMeta)
-class Credentials(credentials.Credentials):
+class Credentials(credentials.Credentials, metaclass=abc.ABCMeta):
     """Async inherited credentials class from google.auth.credentials.
     The added functionality is the before_request call which requires
     async/await syntax.
@@ -84,8 +81,7 @@ class AnonymousCredentials(credentials.AnonymousCredentials, Credentials):
     """
 
 
-@six.add_metaclass(abc.ABCMeta)
-class ReadOnlyScoped(credentials.ReadOnlyScoped):
+class ReadOnlyScoped(credentials.ReadOnlyScoped, metaclass=abc.ABCMeta):
     """Interface for credentials whose scopes can be queried.
 
     OAuth 2.0-based credentials allow limiting access using scopes as described
@@ -171,6 +167,5 @@ def with_scopes_if_required(credentials, scopes):
         return credentials
 
 
-@six.add_metaclass(abc.ABCMeta)
-class Signing(credentials.Signing):
+class Signing(credentials.Signing, metaclass=abc.ABCMeta):
     """Interface for credentials that can cryptographically sign messages."""

google/auth/_default.py

@@ -23,8 +23,6 @@
 import os
 import warnings
 
-import six
-
 from google.auth import environment_vars
 from google.auth import exceptions
 import google.auth.transport._http_client
@@ -115,7 +113,7 @@ def load_credentials_from_file(
             new_exc = exceptions.DefaultCredentialsError(
                 "File {} is not a valid json file.".format(filename), caught_exc
             )
-            six.raise_from(new_exc, caught_exc)
+            raise new_exc from caught_exc
 
     # The type key should indicate that the file is either a service account
     # credentials file or an authorized user credentials file.
@@ -131,7 +129,7 @@ def load_credentials_from_file(
         except ValueError as caught_exc:
             msg = "Failed to load authorized user credentials from {}".format(filename)
             new_exc = exceptions.DefaultCredentialsError(msg, caught_exc)
-            six.raise_from(new_exc, caught_exc)
+            raise new_exc from caught_exc
         if quota_project_id:
             credentials = credentials.with_quota_project(quota_project_id)
         if not credentials.quota_project_id:
@@ -148,7 +146,7 @@ def load_credentials_from_file(
         except ValueError as caught_exc:
             msg = "Failed to load service account credentials from {}".format(filename)
             new_exc = exceptions.DefaultCredentialsError(msg, caught_exc)
-            six.raise_from(new_exc, caught_exc)
+            raise new_exc from caught_exc
         if quota_project_id:
             credentials = credentials.with_quota_project(quota_project_id)
         return credentials, info.get("project_id")

google/auth/_default_async.py

@@ -21,8 +21,6 @@
 import json
 import os
 
-import six
-
 from google.auth import _default
 from google.auth import environment_vars
 from google.auth import exceptions
@@ -63,7 +61,7 @@ def load_credentials_from_file(filename, scopes=None, quota_project_id=None):
             new_exc = exceptions.DefaultCredentialsError(
                 "File {} is not a valid json file.".format(filename), caught_exc
             )
-            six.raise_from(new_exc, caught_exc)
+            raise new_exc from caught_exc
 
     # The type key should indicate that the file is either a service account
     # credentials file or an authorized user credentials file.
@@ -79,7 +77,7 @@ def load_credentials_from_file(filename, scopes=None, quota_project_id=None):
         except ValueError as caught_exc:
             msg = "Failed to load authorized user credentials from {}".format(filename)
             new_exc = exceptions.DefaultCredentialsError(msg, caught_exc)
-            six.raise_from(new_exc, caught_exc)
+            raise new_exc from caught_exc
         if not credentials.quota_project_id:
             _default._warn_about_problematic_credentials(credentials)
         return credentials, None
@@ -94,7 +92,7 @@ def load_credentials_from_file(filename, scopes=None, quota_project_id=None):
         except ValueError as caught_exc:
             msg = "Failed to load service account credentials from {}".format(filename)
             new_exc = exceptions.DefaultCredentialsError(msg, caught_exc)
-            six.raise_from(new_exc, caught_exc)
+            raise new_exc from caught_exc
         return credentials, info.get("project_id")
 
     else:

google/auth/_helpers.py

@@ -17,9 +17,7 @@
 import base64
 import calendar
 import datetime
-
-import six
-from six.moves import urllib
+import urllib
 
 
 CLOCK_SKEW_SECS = 10  # 10 seconds
@@ -84,9 +82,6 @@ def datetime_to_secs(value):
 def to_bytes(value, encoding="utf-8"):
     """Converts a string value to bytes, if necessary.
 
-    Unfortunately, ``six.b`` is insufficient for this task since in
-    Python 2 because it does not modify ``unicode`` objects.
-
     Args:
         value (Union[str, bytes]): The value to be converted.
         encoding (str): The encoding to use to convert unicode to bytes.
@@ -99,8 +94,8 @@ def to_bytes(value, encoding="utf-8"):
     Raises:
         ValueError: If the value could not be converted to bytes.
     """
-    result = value.encode(encoding) if isinstance(value, six.text_type) else value
-    if isinstance(result, six.binary_type):
+    result = value.encode(encoding) if isinstance(value, str) else value
+    if isinstance(result, bytes):
         return result
     else:
         raise ValueError("{0!r} could not be converted to bytes".format(value))
@@ -119,8 +114,8 @@ def from_bytes(value):
     Raises:
         ValueError: If the value could not be converted to unicode.
     """
-    result = value.decode("utf-8") if isinstance(value, six.binary_type) else value
-    if isinstance(result, six.text_type):
+    result = value.decode("utf-8") if isinstance(value, bytes) else value
+    if isinstance(result, str):
         return result
     else:
         raise ValueError("{0!r} could not be converted to unicode".format(value))
@@ -162,7 +157,7 @@ def update_query(url, params, remove=None):
     query_params.update(params)
     # Remove any values specified in remove.
     query_params = {
-        key: value for key, value in six.iteritems(query_params) if key not in remove
+        key: value for key, value in query_params.items() if key not in remove
     }
     # Re-encoded the query string.
     new_query = urllib.parse.urlencode(query_params, doseq=True)

google/auth/_oauth2client.py

@@ -21,8 +21,6 @@
 
 from __future__ import absolute_import
 
-import six
-
 from google.auth import _helpers
 import google.auth.app_engine
 import google.auth.compute_engine
@@ -34,7 +32,7 @@
     import oauth2client.contrib.gce
     import oauth2client.service_account
 except ImportError as caught_exc:
-    six.raise_from(ImportError("oauth2client is not installed."), caught_exc)
+    raise ImportError("oauth2client is not installed.") from caught_exc
 
 try:
     import oauth2client.contrib.appengine  # pytype: disable=import-error
@@ -166,4 +164,4 @@ def convert(credentials):
         return _CLASS_CONVERSION_MAP[credentials_class](credentials)
     except KeyError as caught_exc:
         new_exc = ValueError(_CONVERT_ERROR_TMPL.format(credentials_class))
-        six.raise_from(new_exc, caught_exc)
+        raise new_exc from caught_exc

google/auth/_service_account_info.py

@@ -17,8 +17,6 @@
 import io
 import json
 
-import six
-
 from google.auth import crypt
 
 
@@ -43,7 +41,7 @@ def from_dict(data, require=None):
     """
     keys_needed = set(require if require is not None else [])
 
-    missing = keys_needed.difference(six.iterkeys(data))
+    missing = keys_needed.difference(data)
 
     if missing:
         raise ValueError(

google/auth/aws.py

@@ -39,13 +39,12 @@
 
 import hashlib
 import hmac
+import http.client
 import io
 import json
 import os
 import re
-
-from six.moves import http_client
-from six.moves import urllib
+import urllib
 
 from google.auth import _helpers
 from google.auth import environment_vars
@@ -627,7 +626,7 @@ def _get_metadata_security_credentials(self, request, role_name):
             else response.data
         )
 
-        if response.status != http_client.OK:
+        if response.status != http.client.OK:
             raise exceptions.RefreshError(
                 "Unable to retrieve AWS security credentials", response_body
             )
@@ -666,7 +665,7 @@ def _get_metadata_role_name(self, request):
             else response.data
         )
 
-        if response.status != http_client.OK:
+        if response.status != http.client.OK:
             raise exceptions.RefreshError(
                 "Unable to retrieve AWS role name", response_body
             )

google/auth/compute_engine/_metadata.py

@@ -18,13 +18,11 @@
 """
 
 import datetime
+import http.client
 import json
 import logging
 import os
-
-import six
-from six.moves import http_client
-from six.moves.urllib import parse as urlparse
+from urllib import parse as urlparse
 
 from google.auth import _helpers
 from google.auth import environment_vars
@@ -91,7 +89,7 @@ def ping(request, timeout=_METADATA_DEFAULT_TIMEOUT, retry_count=3):
 
             metadata_flavor = response.headers.get(_METADATA_FLAVOR_HEADER)
             return (
-                response.status == http_client.OK
+                response.status == http.client.OK
                 and metadata_flavor == _METADATA_FLAVOR_VALUE
             )
 
@@ -165,7 +163,7 @@ def get(
             "metadata service. Compute Engine Metadata server unavailable".format(url)
         )
 
-    if response.status == http_client.OK:
+    if response.status == http.client.OK:
         content = _helpers.from_bytes(response.data)
         if response.headers["content-type"] == "application/json":
             try:
@@ -175,7 +173,7 @@ def get(
                     "Received invalid JSON from the Google Compute Engine"
                     "metadata service: {:.20}".format(content)
                 )
-                six.raise_from(new_exc, caught_exc)
+                raise new_exc from caught_exc
         else:
             return content
     else:

google/auth/compute_engine/credentials.py

@@ -21,8 +21,6 @@
 
 import datetime
 
-import six
-
 from google.auth import _helpers
 from google.auth import credentials
 from google.auth import exceptions
@@ -38,7 +36,7 @@ class Credentials(credentials.Scoped, credentials.CredentialsWithQuotaProject):
     These credentials use the Google Compute Engine metadata server to obtain
     OAuth 2.0 access tokens associated with the instance's service account,
     and are also used for Cloud Run, Flex and App Engine (except for the Python
-    2.7 runtime).
+    2.7 runtime, which is supported only on older versions of this library).
 
     For more information about Compute Engine authentication, including how
     to configure scopes, see the `Compute Engine authentication
@@ -114,7 +112,7 @@ def refresh(self, request):
             )
         except exceptions.TransportError as caught_exc:
             new_exc = exceptions.RefreshError(caught_exc)
-            six.raise_from(new_exc, caught_exc)
+            raise new_exc from caught_exc
 
     @property
     def service_account_email(self):
@@ -352,7 +350,7 @@ def _call_metadata_identity_endpoint(self, request):
             id_token = _metadata.get(request, path, params=params)
         except exceptions.TransportError as caught_exc:
             new_exc = exceptions.RefreshError(caught_exc)
-            six.raise_from(new_exc, caught_exc)
+            raise new_exc from caught_exc
 
         _, payload, _, _ = jwt._unverified_decode(id_token)
         return id_token, datetime.datetime.fromtimestamp(payload["exp"])

google/auth/credentials.py

@@ -17,13 +17,10 @@
 
 import abc
 
-import six
-
 from google.auth import _helpers
 
 
-@six.add_metaclass(abc.ABCMeta)
-class Credentials(object):
+class Credentials(object, metaclass=abc.ABCMeta):
     """Base class for all credentials.
 
     All credentials have a :attr:`token` that is used for authentication and
@@ -187,8 +184,7 @@ def before_request(self, request, method, url, headers):
         """Anonymous credentials do nothing to the request."""
 
 
-@six.add_metaclass(abc.ABCMeta)
-class ReadOnlyScoped(object):
+class ReadOnlyScoped(object, metaclass=abc.ABCMeta):
     """Interface for credentials whose scopes can be queried.
 
     OAuth 2.0-based credentials allow limiting access using scopes as described
@@ -329,8 +325,7 @@ def with_scopes_if_required(credentials, scopes, default_scopes=None):
         return credentials
 
 
-@six.add_metaclass(abc.ABCMeta)
-class Signing(object):
+class Signing(object, metaclass=abc.ABCMeta):
     """Interface for credentials that can cryptographically sign messages."""
 
     @abc.abstractmethod