Implement further config validation

Basically just parse the config file before we save it, ensuring that it
can be parsed by `configparser` - the same parser used by Klipper.

This PR depende on the changes from https://github.com/AliceGrey/OctoprintKlipperPlugin/pull/8
in order to send a warning popup when validation fails.

octoprint_klipper/__init__.py

@@ -22,6 +22,7 @@ import os
 from octoprint.util.comm import parse_firmware_line
 from .modules import KlipperLogAnalyzer
 import flask
+import configparser
 
 class KlipperPlugin(
       octoprint.plugin.StartupPlugin,
@@ -116,6 +117,17 @@ class KlipperPlugin(
          try:
             data["config"] = data["config"].encode('utf-8')
 
+            # Basic validation of config file - makes sure it parses
+            try:
+                parser = configparser.RawConfigParser()
+                parser.read_string(data["config"])
+            except configParser.Error as error:
+                self._logger.error(
+                   "Error: Invalid Klipper config file: {}".format(str(error))
+                )
+                self.sendMessage("errorPopUp","warning", "OctoKlipper Settings", "Invalid Klipper config file: " + str(error))
+
+
             f = open(configpath, "w")
             f.write(data["config"])
             f.close()