Dont' infinite loop on errors in readline.

Instead try to show a useful error message.

lib/pry/pry_instance.rb

@@ -522,6 +522,16 @@ class Pry
         self.input = input_stack.pop
       end
       retry
+    # We want to catch exceptions that happen in readline and abort completely,
+    # otherwise we'll likely go round and round the repl-loop and fail every time.
+    rescue RescuableException => e
+      puts "Error: #{e.message}"
+      puts "FATAL: Pry failed to get user input using `#{input.inspect}`."
+      puts "To fix this you may be able to pass input and output file descriptors to pry directly. e.g."
+      puts "  Pry.config.input = STDIN"
+      puts "  Pry.config.output = STDOUT"
+      puts "  binding.pry
+      throw(:breakout)
     end
   end
   private :handle_read_errors