Don't only catch BadRequest key errors but all bad request errors.

docs/config.rst

@@ -89,13 +89,15 @@ The following configuration values are used internally by Flask:
                                   helpful for hairy debugging situations
                                   where you have to find out where an HTTP
                                   exception is coming from.
-``TRAP_BAD_REQUEST_KEY_ERRORS``   Werkzeug's internal data structures that
+``TRAP_BAD_REQUEST_ERRORS``       Werkzeug's internal data structures that
                                   deal with request specific data will
                                   raise special key errors that are also
-                                  bad request exceptions.  By default
-                                  these will be converted into 400
-                                  responses which however can make
-                                  debugging some issues harder.  If this
+                                  bad request exceptions.  Likewise many
+                                  operations can implicitly fail with a
+                                  BadRequest exception for consistency.
+                                  Since it's nice for debugging to know
+                                  why exactly it failed this flag can be
+                                  used to debug those situations.  If this
                                   config is set to ``True`` you will get
                                   a regular traceback instead.
 ================================= =========================================
@@ -132,7 +134,7 @@ The following configuration values are used internally by Flask:
    ``PROPAGATE_EXCEPTIONS``, ``PRESERVE_CONTEXT_ON_EXCEPTION``
 
 .. versionadded:: 0.8
-   ``TRAP_BAD_REQUEST_KEY_ERRORS``, ``TRAP_HTTP_EXCEPTIONS``
+   ``TRAP_BAD_REQUEST_ERRORS``, ``TRAP_HTTP_EXCEPTIONS``
 
 Configuring from Files
 ----------------------

flask/app.py

@@ -216,7 +216,7 @@ class Flask(_PackageBoundObject):
         'LOGGER_NAME':                          None,
         'SERVER_NAME':                          None,
         'MAX_CONTENT_LENGTH':                   None,
-        'TRAP_BAD_REQUEST_KEY_ERRORS':          False,
+        'TRAP_BAD_REQUEST_ERRORS':              False,
         'TRAP_HTTP_EXCEPTIONS':                 False
     })
 
@@ -1054,7 +1054,7 @@ class Flask(_PackageBoundObject):
     def trap_http_exception(self, e):
         """Checks if an HTTP exception should be trapped or not.  By default
         this will return `False` for all exceptions except for a bad request
-        key error if ``TRAP_BAD_REQUEST_KEY_ERRORS`` is set to `True`.  It
+        key error if ``TRAP_BAD_REQUEST_ERRORS`` is set to `True`.  It
         also returns `True` if ``TRAP_HTTP_EXCEPTIONS`` is set to `True`.
 
         This is called for all HTTP exceptions raised by a view function.
@@ -1067,8 +1067,8 @@ class Flask(_PackageBoundObject):
         """
         if self.config['TRAP_HTTP_EXCEPTIONS']:
             return True
-        if self.config['TRAP_BAD_REQUEST_KEY_ERRORS']:
-            return isinstance(e, BadRequest) and isinstance(e, LookupError)
+        if self.config['TRAP_BAD_REQUEST_ERRORS']:
+            return isinstance(e, BadRequest)
         return False
 
     def handle_user_exception(self, e):

tests/flask_tests.py

@@ -601,7 +601,7 @@ class BasicFunctionalityTestCase(unittest.TestCase):
         c = app.test_client()
         assert c.get('/fail').status_code == 400
 
-        app.config['TRAP_BAD_REQUEST_KEY_ERRORS'] = True
+        app.config['TRAP_BAD_REQUEST_ERRORS'] = True
         c = app.test_client()
         try:
             c.get('/fail')