chore(revert): revert preventing normalization (#740)

reverts previous commit for preventing normalization of versioning

setup.py

@@ -15,24 +15,9 @@
 import io
 import os
 
-import setuptools
+from setuptools import find_packages
+from setuptools import setup
 
-# Disable version normalization performed by setuptools.setup()
-# Adding this in even though it works for Python3.x, but does not
-# work for Python 2.7
-try:
-    # Try the approach of using sic(), added in setuptools 46.1.0
-    from setuptools import sic
-except ImportError:
-    # Try the approach of replacing packaging.version.Version
-    sic = lambda v: v
-    try:
-        # setuptools >=39.0.0 uses packaging from setuptools.extern
-        from setuptools.extern import packaging
-    except ImportError:
-        # setuptools <39.0.0 uses packaging from pkg_resources.extern
-        from pkg_resources.extern import packaging
-    packaging.version.Version = packaging.version.LegacyVersion
 
 DEPENDENCIES = (
     "cachetools>=2.0.0,<5.0",
@@ -61,15 +46,15 @@
     exec(fp.read(), version)
 version = version["__version__"]
 
-setuptools.setup(
+setup(
     name="google-auth",
-    version=sic(version),
+    version=version,
     author="Google Cloud Platform",
     author_email="googleapis-packages@google.com",
     description="Google Authentication Library",
     long_description=long_description,
     url="https://github.com/googleapis/google-auth-library-python",
-    packages=setuptools.find_packages(exclude=("tests*", "system_tests*")),
+    packages=find_packages(exclude=("tests*", "system_tests*")),
     namespace_packages=("google",),
     install_requires=DEPENDENCIES,
     extras_require=extras,