Pin google-api-python-client version for agent dependencies in Python2

PiperOrigin-RevId: 315709983
Change-Id: Ia1e2527dcab204003015575843a5e7da6d4cac98

Author: Louis Ye

src/setup.py

@@ -108,7 +108,8 @@ def ReadConfig(section, value, default):
     author='Google Inc.',
     version=version,
     install_requires=[
-        'google-api-python-client',
+        'google-api-python-client==1.8.4'
+        if sys.version_info.major < 3 else 'google-api-python-client',
         'google-auth==1.8.2'
         if sys.version_info.major < 3 else 'google-auth>=1.0.0',
         'google-auth-httplib2',