Catch errors during websocket send

Tidy up the error handling code a little, and substitute out gem paths.

lib/mail_catcher.rb

@@ -60,6 +60,17 @@ module MailCatcher extend self
     end
   end
 
+  def log_exception(message, context, exception)
+    gems_paths = (Gem.path | [Gem.default_dir]).map { |path| Regexp.escape(path) }
+    gems_regexp = %r{(?:#{gems_paths.join('|')})/gems/([^/]+)-([\w.]+)/(.*)}
+    gems_replace = '\1 (\2) \3'
+
+    puts "*** #{message}: #{context.inspect}"
+    puts "    Exception: #{exception}"
+    puts "    Backtrace:", *exception.backtrace.map { |line| "       #{line.sub(gems_regexp, gems_replace)}" }
+    puts "    Please submit this as an issue at http://github.com/sj26/mailcatcher/issues"
+  end
+
   @@defaults = {
     :smtp_ip => '127.0.0.1',
     :smtp_port => '1025',

lib/mail_catcher/smtp.rb

@@ -46,14 +46,8 @@ class MailCatcher::Smtp < EventMachine::Protocols::SmtpServer
     MailCatcher::Mail.add_message current_message
     puts "==> SMTP: Received message from '#{current_message[:sender]}' (#{current_message[:source].length} bytes)"
     true
-  rescue
-    puts "*** Error receiving message: #{current_message.inspect}"
-    puts "    Exception: #{$!}"
-    puts "    Backtrace:"
-    $!.backtrace.each do |line|
-      puts "       #{line}"
-    end
-    puts "    Please submit this as an issue at http://github.com/sj26/mailcatcher/issues"
+  rescue => exception
+    MailCatcher.log_exception("Error receiving message", @current_message, exception)
     false
   ensure
     @current_message = nil

lib/mail_catcher/web/application.rb

@@ -64,8 +64,15 @@ module MailCatcher
         if request.websocket?
           request.websocket!(
             :on_start => proc do |websocket|
-              subscription = Events::MessageAdded.subscribe { |message| websocket.send_message(JSON.generate(message)) }
-              websocket.on_close do |websocket|
+              subscription = Events::MessageAdded.subscribe do |message|
+                begin
+                  websocket.send_message(JSON.generate(message))
+                rescue => exception
+                  MailCatcher.log_exception("Error sending message through websocket", message, exception)
+                end
+              end
+
+              websocket.on_close do |*|
                 Events::MessageAdded.unsubscribe subscription
               end
             end)