Include headers set by BaseEngine() in requests

BaseEngine.construct_request_kwargs() fails to preserve existing
headers set in self.requests by BaseEngine.__init__.  Merge the
new headers with the existing engine headers.  (This was noticed
with 'key' for API access via key.)

Fixes: #353
Signed-off-by: Dan Mick <dan.mick@redhat.com>

Author: dmick

redminelib/engines/base.py

@@ -60,7 +60,11 @@ def construct_request_kwargs(self, method, headers, params, data):
         :param data: (required). Data to send in the body of the request.
         :type data: dict, bytes or file-like object
         """
-        kwargs = dict(self.requests, **{'data': data or {}, 'params': params or {}, 'headers': headers or {}})
+        # headers may be supplied in __init__; merge in any newly-requested headers
+        merged_headers = headers or {}
+        if 'headers' in self.requests:
+            merged_headers = self.requests['headers'] | merged_headers
+        kwargs = dict(self.requests, **{'data': data or {}, 'params': params or {}, 'headers': merged_headers})
 
         if method in ('post', 'put', 'patch') and 'Content-Type' not in kwargs['headers']:
             kwargs['data'] = json.dumps(data)