[travis] Bump to latest versions for non-Linux platforms

Author: frozencemetery

.travis.yml

@@ -30,7 +30,7 @@ jobs:
   # need to explictly define each builder for test due to different os types
   include:
   - stage: test
-    env: DISTRO=debian:stable PYTHON="3" # 3.4, not 3.5
+    env: DISTRO=debian:stable PYTHON="3" # 3.7
 
   - stage: test
     env: DISTRO=debian:stable PYTHON="3" KRB5_VER="heimdal"
@@ -42,6 +42,7 @@ jobs:
   - stage: test
     env: DISTRO=fedora:latest PYTHON="3" FLAKE="yes"
 
+  # Travis defaults to 10.13 (i.e., not latest), so specify osx_image
   - &osx_test
     stage: test
     env: PYTHON="3" KRB5_VER="heimdal" PYENV="3.6.3"
@@ -51,12 +52,12 @@ jobs:
 
   - &win_test
     stage: test
-    env: PYTHON="3" PYENV="3.7.3"
+    env: PYTHON="3" PYENV="3.8.1"
     os: windows
     language: sh  # Windows not supported yet
 
   - <<: *win_test
-    env: PYTHON="3" PYENV="3.6.8"
+    env: PYTHON="3" PYENV="3.7.3"
 
   - stage: deploy latest docs
     script: skip
@@ -122,10 +123,10 @@ jobs:
       - ./.travis/deploy-win.sh
     env:
       - PYTHON="3"
-      - PYENV="3.7.3"
+      - PYENV="3.8.1"
     language: sh # Travis doesn't support python here
 
   - <<: *win_deploy
     env:
       - PYTHON="3"
-      - PYENV="3.6.8"
+      - PYENV="3.7.3"

.travis/lib-setup.sh

@@ -67,7 +67,8 @@ setup::rh::install() {
 }
 
 setup::macos::install() {
-    # install Python from pyenv so we know what version is being used
+    # Install Python from pyenv so we know what version is being used.  This
+    # doesn't work for newer macos.
     pyenv install $PYENV
     pyenv global $PYENV
     virtualenv -p $(pyenv which python) .venv