Clarify error reports indicating they come from Cowboy

src/cowboy_protocol.erl

@@ -495,7 +495,7 @@ handler_init(Req, State=#state{transport=Transport}, Handler, Opts) ->
 	catch Class:Reason ->
 		error_terminate(500, State),
 		error_logger:error_msg(
-			"** Handler ~p terminating in init/3~n"
+			"** Cowboy handler ~p terminating in init/3~n"
 			"   for the reason ~p:~p~n"
 			"** Options were ~p~n"
 			"** Request was ~p~n"
@@ -520,7 +520,7 @@ handler_handle(Req, State, Handler, HandlerState) ->
 			terminate_request(Req2, State, Handler, HandlerState2)
 	catch Class:Reason ->
 		error_logger:error_msg(
-			"** Handler ~p terminating in handle/2~n"
+			"** Cowboy handler ~p terminating in handle/2~n"
 			"   for the reason ~p:~p~n"
 			"** Handler state was ~p~n"
 			"** Request was ~p~n"
@@ -578,7 +578,7 @@ handler_call(Req, State, Handler, HandlerState, Message) ->
 				Handler, HandlerState2)
 	catch Class:Reason ->
 		error_logger:error_msg(
-			"** Handler ~p terminating in info/3~n"
+			"** Cowboy handler ~p terminating in info/3~n"
 			"   for the reason ~p:~p~n"
 			"** Handler state was ~p~n"
 			"** Request was ~p~n"
@@ -595,7 +595,7 @@ handler_terminate(Req, Handler, HandlerState) ->
 		Handler:terminate(cowboy_req:lock(Req), HandlerState)
 	catch Class:Reason ->
 		error_logger:error_msg(
-			"** Handler ~p terminating in terminate/2~n"
+			"** Cowboy handler ~p terminating in terminate/2~n"
 			"   for the reason ~p:~p~n"
 			"** Handler state was ~p~n"
 			"** Request was ~p~n"

src/cowboy_rest.erl

@@ -73,7 +73,7 @@ upgrade(_ListenerPid, Handler, Opts, Req) ->
 	catch Class:Reason ->
 		PLReq = cowboy_req:to_list(Req),
 		error_logger:error_msg(
-			"** Handler ~p terminating in rest_init/2~n"
+			"** Cowboy handler ~p terminating in rest_init/2~n"
 			"   for the reason ~p:~p~n** Options were ~p~n"
 			"** Request was ~p~n** Stacktrace: ~p~n~n",
 			[Handler, Class, Reason, Opts, PLReq, erlang:get_stacktrace()]),

src/cowboy_websocket.erl

@@ -127,7 +127,7 @@ handler_init(State=#state{transport=Transport, handler=Handler, opts=Opts},
 		upgrade_error(Req),
 		PLReq = cowboy_req:to_list(Req),
 		error_logger:error_msg(
-			"** Handler ~p terminating in websocket_init/3~n"
+			"** Cowboy handler ~p terminating in websocket_init/3~n"
 			"   for the reason ~p:~p~n** Options were ~p~n"
 			"** Request was ~p~n** Stacktrace: ~p~n~n",
 			[Handler, Class, Reason, Opts, PLReq, erlang:get_stacktrace()])
@@ -489,7 +489,7 @@ handler_call(State=#state{handler=Handler, opts=Opts}, Req, HandlerState,
 	catch Class:Reason ->
 		PLReq = cowboy_req:to_list(Req),
 		error_logger:error_msg(
-			"** Handler ~p terminating in ~p/3~n"
+			"** Cowboy handler ~p terminating in ~p/3~n"
 			"   for the reason ~p:~p~n** Message was ~p~n"
 			"** Options were ~p~n** Handler state was ~p~n"
 			"** Request was ~p~n** Stacktrace: ~p~n~n",
@@ -549,7 +549,7 @@ handler_terminate(#state{handler=Handler, opts=Opts},
 	catch Class:Reason ->
 		PLReq = cowboy_req:to_list(Req),
 		error_logger:error_msg(
-			"** Handler ~p terminating in websocket_terminate/3~n"
+			"** Cowboy handler ~p terminating in websocket_terminate/3~n"
 			"   for the reason ~p:~p~n** Initial reason was ~p~n"
 			"** Options were ~p~n** Handler state was ~p~n"
 			"** Request was ~p~n** Stacktrace: ~p~n~n",