Check that infile is not a directory

Co-Authored-By: Aliaksei Urbanski <mimworkmail@gmail.com>

Author: LucidOne

src/configobj/__init__.py

@@ -1212,7 +1212,7 @@ def _load(self, infile, configspec):
 
         if isinstance(infile, six.string_types):
             self.filename = infile
-            if os.path.exists(infile):
+            if os.path.exists(infile) and not os.path.isdir(infile):
                 with open(infile, 'rb') as h:
                     content = h.readlines() or []
             elif self.file_error: