Make sure plugins/ contains no symbolic links or other things that aren't regular files (#4579)

tests/sanity/extra/no-unwanted-files.py

@@ -6,6 +6,7 @@ from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type
 
 import os
+import os.path
 import sys
 
 
@@ -38,6 +39,11 @@ def main():
         if any(path.startswith(skip_directory) for skip_directory in skip_directories):
             continue
 
+        if os.path.islink(path):
+            print('%s: is a symbolic link' % (path, ))
+        elif not os.path.isfile(path):
+            print('%s: is not a regular file' % (path, ))
+
         ext = os.path.splitext(path)[1]
 
         if ext in ('.yml', ) and any(path.startswith(yaml_directory) for yaml_directory in yaml_directories):