fix: missing aiohttp error handler

AioHttpApp is handling errors like FlaskApp's common_error_handler

connexion/apps/aiohttp_app.py

@@ -8,15 +8,41 @@
 from aiohttp.test_utils import TestClient, TestServer
 
 from ..apis.aiohttp_api import AioHttpApi
-from ..exceptions import ConnexionException
+from ..exceptions import ConnexionException, ProblemException
+from ..http_facts import HTTP_ERRORS
 from ..lifecycle import ConnexionResponse
+from ..problem import problem
 from ..tests import AbstractClient
-from ..utils import is_json_mimetype
 from .abstract import AbstractApp
 
 logger = logging.getLogger('connexion.aiohttp_app')
 
 
+@web.middleware
+@asyncio.coroutine
+def error_middleware(request, handler):
+    error_response = None
+    try:
+        return (yield from handler(request))
+    except web.HTTPException as ex:
+        if ex.status_code >= 400:
+            error_response = problem(
+                title=HTTP_ERRORS[ex.status_code]["title"],
+                detail=HTTP_ERRORS[ex.status_code]["detail"],
+                status=ex.status_code
+            )
+    except ProblemException as exception:
+        error_response = exception.to_problem()
+    except Exception:
+        error_response = problem(
+            title=HTTP_ERRORS[500]["title"],
+            detail=HTTP_ERRORS[500]["detail"],
+            status=500
+        )
+    if error_response:
+        return (yield from AioHttpApi.get_response(error_response))
+
+
 class AioHttpApp(AbstractApp):
 
     api_cls = AioHttpApi
@@ -27,7 +53,7 @@ def __init__(self, import_name, only_one_api=False, **kwargs):
         self._api_added = False
 
     def create_app(self):
-        return web.Application(debug=self.debug)
+        return web.Application(debug=self.debug, middlewares=[error_middleware])
 
     def get_root_path(self):
         mod = sys.modules.get(self.import_name)
@@ -46,6 +72,7 @@ def get_root_path(self):
         return os.path.dirname(os.path.abspath(filepath))
 
     def set_errors_handlers(self):
+        """error handlers are set in `create_app`."""
         pass
 
     def add_api(self, specification, **kwargs):

connexion/http_facts.py

@@ -2,3 +2,29 @@
     'application/x-www-form-urlencoded',
     'multipart/form-data'
 ]
+
+HTTP_ERRORS = {
+    404: {
+        "title": "Not Found",
+        "detail": 'The requested URL was not found on the server.  '
+                  'If you entered the URL manually please check your spelling and try again.'
+    },
+    405: {
+        "title": "Method Not Allowed",
+        "detail": "The method is not allowed for the requested URL."
+    },
+    500: {
+        "title": "Internal Server Error",
+        "detail": 'The server encountered an internal error and was unable to complete your request.  '
+                  'Either the server is overloaded or there is an error in the application.'
+    },
+    400: {
+        "title": "Bad Request",
+        "detail": "The browser (or proxy) sent a request that this server could not understand."
+    },
+    403: {
+        "title": "Forbidden",
+        "detail": "You don't have the permission to access the requested resource. "
+                  "It is either read-protected or not readable by the server."
+    }
+}