PYTHON-2940 Fix spec tests that require DNSPython (#756)

Author: juliusgeo

test/test_uri_spec.py

@@ -24,7 +24,8 @@
 
 from pymongo.common import INTERNAL_URI_OPTION_NAME_MAP, validate
 from pymongo.compression_support import _HAVE_SNAPPY
-from pymongo.uri_parser import parse_uri
+from pymongo.srv_resolver import _HAVE_DNSPYTHON
+from pymongo.uri_parser import parse_uri, SRV_SCHEME
 from test import clear_warning_registry, unittest
 
 
@@ -92,7 +93,8 @@ def run_scenario(self):
         compressors = (test.get('options') or {}).get('compressors', [])
         if 'snappy' in compressors and not _HAVE_SNAPPY:
             self.skipTest('This test needs the snappy module.')
-
+        if test['uri'].startswith(SRV_SCHEME) and not _HAVE_DNSPYTHON:
+            self.skipTest("This test needs dnspython package.")
         valid = True
         warning = False