Add tests for #382

The examples are not arbitrary: base64 by default ignores characters
that are not in its alphabet. When decoding, the dashes and underscores
are not b64-valid and therefore ignored, resulting in a sequence with
the wrong padding.

server/lib/python/cartodb_services/test/test_googlegeocoder.py

@@ -124,3 +124,13 @@ class GoogleGeocoderTestCase(unittest.TestCase):
             GoogleMapsGeocoder('another_dummy_client_id',
                                'lalala',
                                None)
+
+    def test_credentials_with_dashes_can_be_valid(self, req_mock):
+        GoogleMapsGeocoder('yet_another_dummy_client_id',
+                           'Ola-k-ase---',
+                           None)
+
+    def test_credentials_with_underscores_can_be_valid(self, req_mock):
+        GoogleMapsGeocoder('yet_another_dummy_client_id',
+                           'Ola_k_ase___',
+                           None)