case insensitive search for "json" in content-type headers

modules/swagger-codegen/src/main/resources/python/rest.mustache

@@ -10,6 +10,7 @@ import json
 import ssl
 import certifi
 import logging
+import re
 
 # python 2 and python 3 compatibility library
 from six import iteritems
@@ -121,7 +122,7 @@ class RESTClientObject(object):
             if method in ['POST', 'PUT', 'PATCH', 'OPTIONS', 'DELETE']:
                 if query_params:
                     url += '?' + urlencode(query_params)
-                if headers['Content-Type'].find('json') != -1:
+                if re.search('json', headers['Content-Type'], re.IGNORECASE):
                     request_body = None
                     if body:
                         request_body = json.dumps(body)