docs(python): document adding Python 3.9 support, dropping 3.5 support (#120)

Closes #787

Source-Author: Tres Seaver <tseaver@palladion.com>
Source-Date: Thu Dec 17 16:08:02 2020 -0500
Source-Repo: googleapis/synthtool
Source-Sha: b670a77a454f415d247907908e8ee7943e06d718
Source-Link: https://github.com/googleapis/synthtool/commit/b670a77a454f415d247907908e8ee7943e06d718
diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index 3f971e6..643fbdb 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -21,8 +21,8 @@
 - The feature must be documented in both the API and narrative
   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.
+- The feature must work fully on the following CPython versions:
+  3.6, 3.7, 3.8 and 3.9 on both UNIX and Windows.
 
 - The feature must not add unnecessary dependencies (where
   "unnecessary" is of course subjective, but new dependencies should
@@ -202,25 +202,24 @@
 
 We support:
 
--  `Python 3.5`_
 -  `Python 3.6`_
 -  `Python 3.7`_
 -  `Python 3.8`_
+-  `Python 3.9`_
 
-.. _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/
+.. _Python 3.9: https://docs.python.org/3.9/
 
 
 Supported versions can be found in our ``noxfile.py`` `config`_.
 
 .. _config: https://github.com/googleapis/python-api-core/blob/master/noxfile.py
 
-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`_
diff --git a/synth.metadata b/synth.metadata
index 5885a7d..caf45af 100644
--- a/synth.metadata
+++ b/synth.metadata
@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/python-api-core.git",
-        "sha": "7a38243c351b228d103eee81fc5ae521ad1c930e"
+        "sha": "4e12b76573e2a1726b0a59a5accc99532e010732"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "aa255b15d52b6d8950cca48cfdf58f7d27a60c8a"
+        "sha": "b670a77a454f415d247907908e8ee7943e06d718"
       }
     }
   ],