[Core] Fix aiohttp auto-headers

sdk/core/azure-core/azure/core/pipeline/transport/aiohttp.py

@@ -90,7 +90,8 @@ async def open(self):
         if not self.session and self._session_owner:
             self.session = aiohttp.ClientSession(
                 loop=self._loop,
-                trust_env=self._use_env_settings
+                trust_env=self._use_env_settings,
+                skip_auto_headers=['Content-Type']
             )
         if self.session is not None:
             await self.session.__aenter__()

sdk/core/azure-core/tests/azure_core_asynctests/test_universal_http.py

@@ -48,6 +48,15 @@ async def test_basic_aiohttp():
     assert sender.session is None
     assert response.status_code == 200
 
+@pytest.mark.asyncio
+async def test_aiohttp_auto_headers():
+
+    request = HttpRequest("POST", "https://www.bing.com/")
+    async with AioHttpTransport() as sender:
+        response = await sender.send(request)
+        auto_headers = response.internal_response.request_info.headers
+        assert 'Content-Type' not in auto_headers
+
 @pytest.mark.asyncio
 async def test_basic_async_requests():
 
@@ -77,4 +86,4 @@ async def do():
             assert response.body() is not None
 
     response = trio.run(do)
-    assert response.status_code == 200
+    assert response.status_code == 200

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

@@ -46,3 +46,10 @@ def thread_body(local_sender):
     with concurrent.futures.ThreadPoolExecutor(max_workers=1) as executor:
         future = executor.submit(thread_body, sender)
         assert future.result()
+
+def test_requests_auto_headers():
+    request = HttpRequest("POST", "https://www.bing.com/")
+    with RequestsTransport() as sender:
+        response = sender.send(request)
+        auto_headers = response.internal_response.request.headers
+        assert 'Content-Type' not in auto_headers