DOC: add more helpful error message when accidentally importing pandas from source directory, address GH #250

Author: wesm

pandas/__init__.py

@@ -6,6 +6,16 @@
 
 import numpy as np
 
+try:
+    import pandas._tseries as lib
+except Exception, e:
+    if 'No module named' in e.message:
+        raise ImportError('C extensions not built: if you installed already '
+                          'verify that you are not importing from the source '
+                          'directory')
+    else:
+        raise
+
 from pandas.version import version as __version__
 from pandas.info import __doc__