add missing urllib submodules imports

Author: Gaetano Guerriero

pydruid/client.py

@@ -15,7 +15,8 @@
 #
 import json
 import re
-import urllib
+import urllib.error
+import urllib.request
 from base64 import b64encode
 
 from pydruid.query import QueryBuilder

tests/test_client.py

@@ -1,6 +1,6 @@
 # -*- coding: UTF-8 -*-
 import textwrap
-import urllib
+import urllib.error
 from io import StringIO
 from unittest.mock import Mock, patch
 
@@ -89,8 +89,8 @@ def test_druid_returns_html_error(self, mock_urlopen):
             str(e.value)
             == textwrap.dedent(
                 """
-            HTTP Error 500: Internal Server Error 
-             Druid Error: javax.servlet.ServletException: java.lang.OutOfMemoryError: GC overhead limit exceeded 
+            HTTP Error 500: Internal Server Error
+             Druid Error: javax.servlet.ServletException: java.lang.OutOfMemoryError: GC overhead limit exceeded
              Query is: {
                 "aggregations": [
                     {