patch 8.0.0240: failure with one build on CI

Problem:    The clang build on CI fails with one configuration.
Solution:   Redo a previous patch that was accidentally reverted.
diff --git a/.travis.yml b/.travis.yml
index 73aac5a..44e320c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -75,8 +75,10 @@
       - cscope
 
 before_install:
-  - pip install --user cpp-coveralls
-  - pip install --user requests[security]
+  - if [ "$COVERAGE" = "yes" ]; then pip install --user cpp-coveralls; fi
+    # needed for https support for coveralls
+    # building cffi only works with gcc, not with clang
+  - if [ "$COVERAGE" = "yes" ]; then CC=gcc pip install --user pyopenssl ndg-httpsclient pyasn1; fi
     # Lua is not installed on Travis OSX
   - if [ "$TRAVIS_OS_NAME" = "osx" ]; then brew install lua; export LUA_PREFIX=/usr/local; fi