Make possible testing of libraries when multiple repos are present

When the TEST_LIBS is set to 'y', tests have been broken as the
utils/library_path.py returned string like:
   path_to_repo1,path_to_repo2

When running pytest this lead just into the error msg "file not found".
Just use the " " separator so tests could be executed again.

utils/library_path.py

@@ -12,4 +12,4 @@
     repos = find_and_scan_repositories(BASE_REPO, include_locals=True)
     repos.load()
 
-    print(','.join(repos.libraries))
+    print(' '.join(repos.libraries))