CI: Update python pins - 3.7 is main version and add 3.9-dev (#707)

Author: snowman2

.travis.yml

@@ -22,28 +22,27 @@ env:
 
 matrix:
   include:
+    - python: 3.6.12
     - language: cpp
       os: osx
       env:
-        - PYTHON=3.6.8
-    - python: 3.6
-    - python: 3.6
+        - PYTHON=3.7.8
+    - python: 3.7.9
+    - python: 3.7.9
       env:
         - PROJ_NETWORK=ON
         - PROJ_DEBUG=3
-    - python: 3.6
+    - python: 3.7.9
       env:
         - PROJSYNC=ALL
-    - python: 3.6
+    - python: 3.7.9
       env:
         - PYPROJ_GLOBAL_CONTEXT=ON
-    - python: 3.7.2
+    - python: 3.7.9
       env:
         - DOC=true
-    - python: 3.8
-    # - python: 3.8
-    #   env:
-    #     - PROJSOURCE=git
+    - python: 3.8.5
+    - python: 3.9-dev
     # - python: "nightly"
     #   env:
     #     - PROJSOURCE=git
@@ -52,9 +51,6 @@ matrix:
     # - python: "nightly"
     #   env:
     #     - PROJSOURCE=git
-    # - python: 3.8
-    #   env:
-    #     - PROJSOURCE=git
 
 
 before_install:
@@ -67,6 +63,7 @@ before_install:
       # virtualenv doesn't work without pyenv knowledge. venv in Python 3.3
       # doesn't provide Pip by default. So, use `pyenv-virtualenv <https://github.com/yyuu/pyenv-virtualenv/blob/master/README.md>`_.
       brew install pyenv-virtualenv
+      pyenv install --list | grep "3.7"
       pyenv install $PYTHON
       # I would expect something like ``pyenv init; pyenv local $PYTHON`` or
       # ``pyenv shell $PYTHON`` would work, but ``pyenv init`` doesn't seem to

appveyor.yml

@@ -18,14 +18,14 @@ environment:
     # build is limited to 60 minutes, without caching each build takes 10-30 minutes
     # with caching build takes less than 1 minute
     - PYTHON: "C:\\Python36-x64"
-      PYTHON_VERSION: "3.6"
+      PYTHON_VERSION: "3.7"
       PYTHON_ARCH: "64"
       VS_VERSION: Visual Studio 14
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
       PROJSOURCE: git
       BUILD_SHARED_LIBS: ON
   # - PYTHON: "C:\\Python37-x64"
-    #   PYTHON_VERSION: "3.7"
+    #   PYTHON_VERSION: "3.8"
     #   PYTHON_ARCH: "64"
     #   VS_VERSION: Visual Studio 14
     #   APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015