Updated the default rescue response (i.e when exception or bad internal error occurs).

Factorized the implementation in WGI_RESCUE_EXECUTION, and now by redefining the `WGI_EXECUTION.execute_rescue (...)` procedure, it is possible to have a custom response on such rescued execution.

library/server/ewsgi/specification/connector/wgi_execution.e

@@ -42,6 +42,14 @@ feature -- Execution
 			is_valid_end_of_execution: is_valid_end_of_execution
 		end
 
+feature {WGI_EXPORTER, WGI_CONNECTOR} -- Execution: rescue
+
+	execute_rescue (e: detachable EXCEPTION)
+			-- Execute on rescue.
+		do
+			(create {WGI_RESCUE_EXECUTION}).execute (request, response, e)
+		end
+
 feature -- Status report
 
 	is_valid_end_of_execution: BOOLEAN

library/server/ewsgi/specification/connector/wgi_rescue_execution.e

@@ -0,0 +1,46 @@
+note
+	description: "Execution when an exception occurred."
+	date: "$Date$"
+	revision: "$Revision$"
+
+class
+	WGI_RESCUE_EXECUTION
+
+inherit
+	WGI_EXPORTER
+
+	SHARED_HTML_ENCODER
+
+feature -- Execution
+
+	execute (req: detachable WGI_REQUEST; res: detachable WGI_RESPONSE; e: detachable EXCEPTION)
+			-- Exception or internal error occurred, return the eventual trace
+			-- as response.
+			-- `req` and `res` may be available for processing.
+		local
+			s: STRING
+		do
+			if 
+				res /= Void and then
+				e /= Void and then 
+				attached e.trace as l_trace 
+			then
+				if not res.status_is_set then
+					res.set_status_code ({HTTP_STATUS_CODE}.internal_server_error, Void)
+				end
+				create s.make_empty
+				s.append ("<pre>")
+				s.append (html_encoder.encoded_string (l_trace))
+				s.append ("</pre>")
+				if not res.header_committed then
+						-- Overwrite any header previously set.
+					res.put_header_text ("Content-Type: text/html%R%NContent-Length: " + s.count.out + "%R%N%R%N")
+				end
+				if res.message_writable then
+					res.put_string (s)
+				end
+				res.push
+			end
+		end		
+
+end