Use proper python2 compatiable string check

Author: hwalinga

pandas/core/common.py

@@ -69,7 +69,7 @@ def consensus_name_attr(objs):
 def clean_column_name_with_spaces(name):
     """Check if name contains any spaces, if it contains any spaces
     the spaces will be removed and an underscore suffix is added."""
-    if not isinstance(name, str) or " " not in name:
+    if not isinstance(name, compat.string_types) or " " not in name:
         return name
     return name.replace(" ", "_") + "_"