fix: Pass custom keyword arguments to client.get in the from_wsgi…

… loader

To match the behavior of `from_uri`. They should be the same, since they contact the application under test

docs/changelog.rst

@@ -10,6 +10,7 @@ Fixed
 ~~~~~
 
 - Support for custom loaders in ``runner``. Now all built-in loaders are supported as an argument to ``runner.prepare``. `#496`_
+- ``from_wsgi`` loader accept custom keyword arguments that will be passed to ``client.get`` when accessing the schema. `#497`_
 
 `1.1.1`_ - 2020-04-12
 ---------------------
@@ -897,6 +898,7 @@ Fixed
 .. _0.3.0: https://github.com/kiwicom/schemathesis/compare/v0.2.0...v0.3.0
 .. _0.2.0: https://github.com/kiwicom/schemathesis/compare/v0.1.0...v0.2.0
 
+.. _#497: https://github.com/kiwicom/schemathesis/issues/497
 .. _#496: https://github.com/kiwicom/schemathesis/issues/496
 .. _#489: https://github.com/kiwicom/schemathesis/issues/489
 .. _#473: https://github.com/kiwicom/schemathesis/issues/473

src/schemathesis/loaders.py

@@ -171,8 +171,9 @@ def from_wsgi(
     validate_schema: bool = True,
     **kwargs: Any,
 ) -> BaseSchema:
+    kwargs.setdefault("headers", {}).setdefault("User-Agent", USER_AGENT)
     client = Client(app, WSGIResponse)
-    response = client.get(schema_path, headers={"User-Agent": USER_AGENT})
+    response = client.get(schema_path, **kwargs)
     # Raising exception to provide unified behavior
     # E.g. it will be handled in CLI - a proper error message will be shown
     if 400 <= response.status_code < 600: