CLN: Add NotImplementedError to DataReader

If requested data source hasn't been implemented.

Author: davidastephens

pandas_datareader/data.py

@@ -90,7 +90,9 @@ def DataReader(name, data_source=None, start=None, end=None,
         return get_data_fred(name, start, end)
     elif data_source == "famafrench":
         return get_data_famafrench(name)
-
+    else:
+        raise NotImplementedError(
+                "data_source=%r is not implemented" % data_source)
 
 def _sanitize_dates(start, end):
     from pandas.core.datetools import to_datetime

pandas_datareader/tests/test_data.py

@@ -471,6 +471,9 @@ def test_read_famafrench(self):
             assert ff
             assert isinstance(ff, dict)
 
+    def test_not_implemented(self):
+        self.assertRaises(NotImplementedError, DataReader, "NA", "NA")
+
 
 class TestFred(tm.TestCase):
     def test_fred(self):