PYTHON-2560 Fix HTTPSConnection typechecking

Author: ShaneHarvey

test/asynchronous/test_encryption.py

@@ -2875,7 +2875,7 @@ async def asyncSetUp(self):
     async def http_post(self, path, data=None):
         # Note, the connection to the mock server needs to be closed after
         # each request because the server is single threaded.
-        ctx = get_ssl_context(
+        ctx: ssl.SSLContext = get_ssl_context(
             CLIENT_PEM,  # certfile
             None,  # passphrase
             CA_PEM,  # ca_certs

test/test_encryption.py

@@ -2857,7 +2857,7 @@ def setUp(self):
     def http_post(self, path, data=None):
         # Note, the connection to the mock server needs to be closed after
         # each request because the server is single threaded.
-        ctx = get_ssl_context(
+        ctx: ssl.SSLContext = get_ssl_context(
             CLIENT_PEM,  # certfile
             None,  # passphrase
             CA_PEM,  # ca_certs