Require network in CI builds

.travis.yml

@@ -63,6 +63,7 @@ install:
 - "! grep pyc setuptools.egg-info/SOURCES.txt"
 
 script:
+  - export NETWORK_REQUIRED=1
   - |
     ( # Run testsuite.
       if [ -z "$DISABLE_COVERAGE" ]

appveyor.yml

@@ -3,6 +3,7 @@ clone_depth: 50
 environment:
 
   APPVEYOR: True
+  NETWORK_REQUIRED: True
   CODECOV_ENV: APPVEYOR_JOB_NAME
 
   matrix:

tox.ini

@@ -18,7 +18,7 @@ list_dependencies_command={envbindir}/pip freeze
 setenv=COVERAGE_FILE={toxworkdir}/.coverage.{envname}
 # TODO: The passed environment variables came from copying other tox.ini files
 # These should probably be individually annotated to explain what needs them.
-passenv=APPDATA HOMEDRIVE HOMEPATH windir APPVEYOR APPVEYOR_* CI CODECOV_* TRAVIS TRAVIS_*
+passenv=APPDATA HOMEDRIVE HOMEPATH windir APPVEYOR APPVEYOR_* CI CODECOV_* TRAVIS TRAVIS_* NETWORK_REQUIRED
 commands=pytest --cov-config={toxinidir}/tox.ini --cov-report= {posargs}
 usedevelop=True