feat: add support for Python 3.9, drop support for Python 3.5 (#55)

CONTRIBUTING.rst

@@ -22,7 +22,7 @@ In order to add a feature:
   documentation.
 
 - The feature must work fully on the following CPython versions:  2.7,
-  3.5, 3.6, 3.7 and 3.8 on both UNIX and Windows.
+  3.6, 3.7 and 3.8 on both UNIX and Windows.
 
 - The feature must not add unnecessary dependencies (where
   "unnecessary" is of course subjective, but new dependencies should
@@ -156,7 +156,7 @@ Running System Tests
     `docs <https://cloud.google.com/storage/docs/authentication#generating-a-private-key>`__
     for more details.
 
-- Once you have downloaded your json keys, set the environment variable 
+- Once you have downloaded your json keys, set the environment variable
   ``GOOGLE_APPLICATION_CREDENTIALS`` to the absolute path of the json file::
 
    $ export GOOGLE_APPLICATION_CREDENTIALS="/Users/<your_username>/path/to/app_credentials.json"
@@ -202,12 +202,10 @@ Supported Python Versions
 
 We support:
 
--  `Python 3.5`_
 -  `Python 3.6`_
 -  `Python 3.7`_
 -  `Python 3.8`_
 
-.. _Python 3.5: https://docs.python.org/3.5/
 .. _Python 3.6: https://docs.python.org/3.6/
 .. _Python 3.7: https://docs.python.org/3.7/
 .. _Python 3.8: https://docs.python.org/3.8/
@@ -220,7 +218,7 @@ Supported versions can be found in our ``noxfile.py`` `config`_.
 Python 2.7 support is deprecated. All code changes should maintain Python 2.7 compatibility until January 1, 2020.
 
 We also explicitly decided to support Python 3 beginning with version
-3.5. Reasons for this include:
+3.6. Reasons for this include:
 
 -  Encouraging use of newest versions of Python 3
 -  Taking the lead of `prominent`_ open-source `projects`_

README.rst

@@ -1,7 +1,7 @@
 Core Helpers for Google Cloud Python Client Library
 ===================================================
 
-|pypi| |versions| 
+|pypi| |versions|
 
 This library is not meant to stand-alone. Instead it defines
 common helpers (e.g. base ``Client`` classes) used by all of the
@@ -32,7 +32,7 @@ to `Python Development Environment Setup Guide`_ for Google Cloud Platform.
 
 Supported Python Versions
 -------------------------
-Python >= 3.5
+Python >= 3.6
 
 Deprecated Python Versions
 --------------------------

noxfile.py

@@ -31,19 +31,12 @@ def default(session):
     run the tests.
     """
     constraints_path = os.path.join(
-        CURRENT_DIRECTORY,
-        "testing",
-        "constraints-{}.txt".format(session.python)
+        CURRENT_DIRECTORY, "testing", "constraints-{}.txt".format(session.python)
     )
 
     # Install all test dependencies, then install local packages in-place.
     session.install(
-        "mock",
-        "pytest",
-        "pytest-cov",
-        "grpcio >= 1.0.2",
-        "-c",
-        constraints_path
+        "mock", "pytest", "pytest-cov", "grpcio >= 1.0.2", "-c", constraints_path
     )
     session.install("-e", ".", "-c", constraints_path)
 
@@ -62,7 +55,7 @@ def default(session):
     )
 
 
-@nox.session(python=["2.7", "3.5", "3.6", "3.7", "3.8"])
+@nox.session(python=["2.7", "3.6", "3.7", "3.8", "3.9"])
 def unit(session):
     """Default unit test session."""
     default(session)
@@ -99,6 +92,7 @@ def cover(session):
     session.run("coverage", "report", "--show-missing", "--fail-under=100")
     session.run("coverage", "erase")
 
+
 @nox.session(python=DEFAULT_PYTHON_VERSION)
 def docs(session):
     """Build the docs for this library."""

setup.py

@@ -43,7 +43,7 @@
 version = {}
 with open(os.path.join(package_root, "google/cloud/version.py")) as fp:
     exec(fp.read(), version)
-version = version['__version__']
+version = version["__version__"]
 
 readme_filename = os.path.join(package_root, "README.rst")
 with io.open(readme_filename, encoding="utf-8") as readme_file:
@@ -78,10 +78,10 @@
         "Programming Language :: Python :: 2",
         "Programming Language :: Python :: 2.7",
         "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
         "Operating System :: OS Independent",
         "Topic :: Internet",
     ],