fix: drop python 3.6 (#456)

* fix: drop python 3.6

* remove testing/constraints-3.6.txt

* update version in .readthedocs.yml

.github/sync-repo-settings.yaml

@@ -7,9 +7,6 @@ branchProtectionRules:
   requiredStatusCheckContexts:
     - 'style-check'
     - 'docs'
-    - 'unit (3.6, cpp)'
-    - 'unit (3.6, python)'
-    - 'unit (3.6, upb)'
     - 'unit (3.7, cpp)'
     - 'unit (3.7, python)'
     - 'unit (3.7, upb)'

.github/workflows/tests.yml

@@ -42,7 +42,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python: ['3.6', '3.7', '3.8', '3.9', '3.10', '3.11', '3.12', '3.13']
+        python: ['3.7', '3.8', '3.9', '3.10', '3.11', '3.12', '3.13']
         variant: ['cpp', 'python', 'upb']
         # TODO(https://github.com/googleapis/proto-plus-python/issues/389):
         # Remove the 'cpp' implementation once support for Protobuf 3.x is dropped.

.readthedocs.yml

@@ -3,4 +3,4 @@ build:
   image: latest
 python:
   pip_install: true
-  version: 3.6
+  version: 3.9

noxfile.py

@@ -22,7 +22,6 @@
 
 
 PYTHON_VERSIONS = [
-    "3.6",
     "3.7",
     "3.8",
     "3.9",

setup.py

@@ -48,15 +48,14 @@
             "google-api-core >= 1.31.5",
         ],
     },
-    python_requires=">=3.6",
+    python_requires=">=3.7",
     classifiers=[
         "Development Status :: 5 - Production/Stable",
         "Environment :: Console",
         "Intended Audience :: Developers",
         "License :: OSI Approved :: Apache Software License",
         "Operating System :: POSIX",
         "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",