Set repsonse encoding to UTF-8 to avoid chardet

The performance of the default chardet used by requests can be very poor and since the JSON is UTF-8 we can avoid going throught that detection.

Author: ricellis

CHANGES.md

@@ -1,3 +1,7 @@
+# Unreleased
+
+- [FIXED] A performance regression deserializing JSON in version 2.10.1.
+
 # 2.10.1 (2018-11-16)
 
 - [FIXED] Unexpected keyword argument errors when using the library with the

src/cloudant/_common_util.py

@@ -288,6 +288,8 @@ def response_to_json_dict(response, **kwargs):
 
     :returns: dict of JSON response
     """
+    if response.encoding is None:
+        response.encoding = 'utf-8'
     return json.loads(response.text, **kwargs)
 
 # Classes