Fix rapid7#4273, print error in create_session

Fix rapid7#4273

Author: wchen-r7

lib/msf/core/handler.rb

@@ -189,7 +189,14 @@ def create_session(conn, opts={})
     # If the payload we merged in with has an associated session factory,
     # allocate a new session.
     if (self.session)
-      s = self.session.new(conn, opts)
+      begin
+        s = self.session.new(conn, opts)
+      rescue ::Exception => e
+        # We just wanna show and log the error, not trying to swallow it.
+        print_error("#{e.class} #{e.message}")
+        elog("#{e.class} #{e.message}\n#{e.backtrace * "\n"}")
+        raise e
+      end
 
       # Pass along the framework context
       s.framework = framework