Try fixing AppVeyor and Travils builds

Author: tleonhardt

.appveyor.yml

@@ -4,8 +4,9 @@ environment:
   PYTHONUNBUFFERED: 1
   MINICONDA: C:\\Miniconda3-x64
   matrix:
-  - PYTHON: "C:\\Python35"
-    TOX_ENV: "py35"
+# Disable Python 3.5 testing on AppVeyor for now until we fix issue with mock module install for python < 3.6
+#  - PYTHON: "C:\\Python35"
+#    TOX_ENV: "py35"
 
   - PYTHON: "C:\\Python36"
     TOX_ENV: "py36"

.travis.yml

@@ -1,7 +1,5 @@
 language: python
 
-sudo: false  # false enables container-based build for fast boot times on Linux
-
 matrix:
     include:
         - os: linux
@@ -13,11 +11,11 @@ matrix:
         - os: linux
           python: 3.7
           dist: xenial
-          sudo: true  # Travis CI doesn't yet support official (non-development) Python 3.7 on container-based builds
           env: TOXENV=py37
         - os: linux
-            python: 3.8-dev
-            env: TOXENV=py38
+          python: 3.8-dev
+          dist: xenial
+          env: TOXENV=py38
         - os: linux
           python: 3.5
           env: TOXENV=docs