Encoding JSON requests to bytes for urllib3 to handle; ensuring same with testing.

AUTHORS.rst

@@ -165,3 +165,4 @@ Patches and Suggestions
 - Brian Samek (`@bsamek <https://github.com/bsamek>`_)
 - Dmitry Dygalo (`@Stranger6667 <https://github.com/Stranger6667>`_)
 - piotrjurkiewicz
+- Jesse Shapiro <jesse@jesseshapiro.net> (`@haikuginger <https://github.com/haikuginger>`_)

requests/models.py

@@ -420,8 +420,11 @@ class PreparedRequest(RequestEncodingMixin, RequestHooksMixin):
         length = None
 
         if not data and json is not None:
-            content_type = 'application/json'
-            body = complexjson.dumps(json)
+            # When urllib3 uses pyOpenSSL, it can only resume large uploads
+            # properly if receiving a bytes-like object. In Python 2, json.dumps()
+            # returns just that, but Python 3 returns a Unicode string.
+            content_type = 'application/json; charset=utf-8'
+            body = complexjson.dumps(json).encode('utf-8')
 
         is_stream = all([
             hasattr(data, '__iter__'),

tests/test_requests.py

@@ -1516,6 +1516,18 @@ class RedirectSession(SessionRedirectMixin):
         return string
 
 
+def test_json_encodes_as_bytes():
+    # urllib3 expects bodies as bytes-like objects
+    body = {"key": "value"}
+    p = PreparedRequest()
+    p.prepare(
+        method='GET',
+        url='https://www.example.com/',
+        json='body'
+    )
+    assert isinstance(p.body, bytes)
+
+
 def test_requests_are_updated_each_time(httpbin):
     session = RedirectSession([303, 307])
     prep = requests.Request('POST', httpbin('post')).prepare()