[rest] fix str check in content kwarg to be six.string_types check fo…

…r 2.7 (Azure#21550)

sdk/core/azure-core/CHANGELOG.md

@@ -17,8 +17,7 @@
   rather than silently truncating data in case the underlying tcp connection is closed prematurely. 
   (thanks to @jochen-ott-by for the contribution)   #20412
 - UnboundLocalError when SansIOHTTPPolicy handles an exception    #15222
-
-### Other Changes
+- Add default content type header of `text/plain` and content length header for users who pass unicode strings to the `content` kwarg of `HttpRequest` in 2.7  #21550
 
 ## 1.19.1 (2021-11-01)
 

sdk/core/azure-core/azure/core/rest/_helpers.py

@@ -134,7 +134,7 @@ def _shared_set_content_body(content):
     if isinstance(content, ET.Element):
         # XML body
         return set_xml_body(content)
-    if isinstance(content, (str, bytes)):
+    if isinstance(content, (six.string_types, bytes)):
         headers = {}
         body = content
         if isinstance(content, six.string_types):

sdk/core/azure-core/tests/test_rest_http_request.py

@@ -255,6 +255,17 @@ def test_data_str_input():
     assert len(request.headers) == 1
     assert request.headers['Content-Type'] == 'application/x-www-form-urlencoded'
 
+def test_content_str_input():
+    requests = [
+        HttpRequest("POST", "/fake", content="hello, world!"),
+        HttpRequest("POST", "/fake", content=u"hello, world!"),
+    ]
+    for request in requests:
+        assert len(request.headers) == 2
+        assert request.headers["Content-Type"] == "text/plain"
+        assert request.headers["Content-Length"] == "13"
+        assert request.content == "hello, world!"
+
 @pytest.mark.parametrize(("value"), (object(), {"key": "value"}))
 def test_multipart_invalid_value(value):