[BUG] [Python] Attribute error when using auth header (#21)

* Wrong header variable type

* Generate Sample

Co-authored-by: Thomas Pfeiffer <thomas.pfeiffer@thalesaleniaspace.com>

Author: totothekiller

modules/openapi-json-schema-generator/src/main/resources/python/api_client.handlebars

@@ -1047,7 +1047,7 @@ class ApiClient:
     ) -> urllib3.HTTPResponse:
 
         # header parameters
-        headers = headers or {}
+        headers = headers or HTTPHeaderDict()
         headers.update(self.default_headers)
         if self.cookie:
             headers['Cookie'] = self.cookie

samples/openapi3/client/3_0_3_unit_test/python/unit_test_api/api_client.py

@@ -1048,7 +1048,7 @@ def __call_api(
     ) -> urllib3.HTTPResponse:
 
         # header parameters
-        headers = headers or {}
+        headers = headers or HTTPHeaderDict()
         headers.update(self.default_headers)
         if self.cookie:
             headers['Cookie'] = self.cookie

samples/openapi3/client/features/nonCompliantUseDiscriminatorIfCompositionFails/python/this_package/api_client.py

@@ -1048,7 +1048,7 @@ def __call_api(
     ) -> urllib3.HTTPResponse:
 
         # header parameters
-        headers = headers or {}
+        headers = headers or HTTPHeaderDict()
         headers.update(self.default_headers)
         if self.cookie:
             headers['Cookie'] = self.cookie

samples/openapi3/client/petstore/python/petstore_api/api_client.py

@@ -1048,7 +1048,7 @@ def __call_api(
     ) -> urllib3.HTTPResponse:
 
         # header parameters
-        headers = headers or {}
+        headers = headers or HTTPHeaderDict()
         headers.update(self.default_headers)
         if self.cookie:
             headers['Cookie'] = self.cookie