Pass urllib3.SKIP_HEADER when headers should be unsetbug/5671

urllib3 introduced some default headers and a way to skip them if
desired. Let's use that sentinel value to pass along information about
Requests' users desire to skip those headers as well.

Closes gh-5671

1 files changed, 15 insertions, 7 deletions

diff --git a/tests/test_requests.py b/tests/test_requests.py
index 5b6a7f58..6a0727b8 100644
--- a/tests/test_requests.py
+++ b/tests/test_requests.py
@@ -17,10 +17,15 @@ import pytest
 from requests.adapters import HTTPAdapter
 from requests.auth import HTTPDigestAuth, _basic_auth_str
 from requests.compat import (
-    Morsel, cookielib, getproxies, str, urlparse,
-    builtin_str)
-from requests.cookies import (
-    cookiejar_from_dict, morsel_to_cookie)
+    Morsel,
+    cookielib,
+    getproxies,
+    str,
+    urlparse,
+    builtin_str,
+    SKIP_HEADER,
+)
+from requests.cookies import cookiejar_from_dict, morsel_to_cookie
 from requests.exceptions import (
     ConnectionError, ConnectTimeout, InvalidSchema, InvalidURL,
     MissingSchema, ReadTimeout, Timeout, RetryError, TooManyRedirects,
@@ -438,10 +443,13 @@ class TestRequests:
     def test_headers_on_session_with_None_are_not_sent(self, httpbin):
         """Do not send headers in Session.headers with None values."""
         ses = requests.Session()
-        ses.headers['Accept-Encoding'] = None
-        req = requests.Request('GET', httpbin('get'))
+        ses.headers["Accept-Encoding"] = None
+        req = requests.Request("GET", httpbin("get"))
         prep = ses.prepare_request(req)
-        assert 'Accept-Encoding' not in prep.headers
+        if not SKIP_HEADER:
+            assert "Accept-Encoding" not in prep.headers
+        else:
+            assert SKIP_HEADER == prep.headers["Accept-Encoding"]
 
     def test_headers_preserve_order(self, httpbin):
         """Preserve order when headers provided as OrderedDict."""