travis: Fix vici Python tests when using Clang

For some reason the clang binary that's installed in an uncommon
directory could not be found anymore when installing packages via pip for
the last couple of builds. While the directory is obviously contained in PATH,
using `sudo -E` didn't help. So we now install the Python packages in the
user's home directory to avoid having to use sudo.

scripts/test.sh

@@ -177,7 +177,7 @@ if test "$1" = "deps"; then
 fi
 
 if test "$1" = "pydeps"; then
-	test -z "$PYDEPS" || sudo pip -q install $PYDEPS
+	test -z "$PYDEPS" || pip -q install --user $PYDEPS
 	exit $?
 fi