travis-ci: Fix "with_system_site_packages"

The "with_system_site_packages" virtualenv seems to be missing the
pymodules directory containing python modules installed with the
python-support debian helper. So we use the default environment and
manually add the references to the system-wide python packages.

.travis.yml

@@ -32,8 +32,8 @@ matrix:
           packages: *build_deps_optional
 
     - python: "2.7"
-    - python: "2.7_with_system_site_packages"
-      env: WITH_OPTIONAL_DEPS=yes TEST_SPHINX=yes
+    - python: "2.7"
+      env: WITH_OPTIONAL_DEPS=yes WITH_SYSTEM_SITE_PACKAGES=yes TEST_SPHINX=yes
       addons:
         apt:
           packages: [*build_deps_optional, python-gamin, python-selinux]

testsuite/install.sh

@@ -2,6 +2,7 @@
 
 # install script for Travis-CI
 PYVER=$(python -c 'import sys;print(".".join(str(v) for v in sys.version_info[0:2]))')
+SITE_PACKAGES=$(python -c 'from distutils.sysconfig import get_python_lib; print(get_python_lib())')
 
 if [[ ${PYVER:0:1} == "2" && $PYVER != "2.7" && $PYVER != "2.6" ]]; then
     pip install -r testsuite/requirements-legacy.txt
@@ -46,6 +47,15 @@ else
     fi
 fi
 
+# Use system site-packages and pymodules
+if [[ "$WITH_SYSTEM_SITE_PACKAGES" == "yes" ]]; then
+     cat <<EOF > "$SITE_PACKAGES/system-packages.pth"
+/usr/lib/python$PYVER/site-packages/
+/usr/lib/python$PYVER/dist-packages/
+/usr/lib/pymodules/python$PYVER/
+EOF
+fi
+
 # Setup the local xml schema cache
 download_schema() {
     if [[ ! -e "$1" ]]; then