Virtual printer now supports resend repetitions

If a new config setting is set, the virtual printer will now
resend the same resend request twice to allow testing the
comm layer behaviour in OctoPrint for being able to cope with
these possible repetitions like they can happen with Repetier.

src/octoprint/plugins/virtual_printer/virtual.py

@@ -314,8 +314,13 @@ class VirtualPrinter(object):
 			else:
 				self._send("Error: expected line %d got %d" % (expected, actual))
 
-			self._send("Resend:%d" % expected)
-			self._send("ok")
+			def request_resend():
+				self._send("Resend:%d" % expected)
+				self._send("ok")
+
+			if settings().getBoolean(["devel", "virtualPrinter", "repetierStyleResends"]):
+				request_resend()
+			request_resend()
 
 	def _debugTrigger(self, data):
 		if data == "action_pause":

src/octoprint/settings.py

@@ -283,6 +283,7 @@ default_settings = {
 			},
 			"hasBed": True,
 			"repetierStyleTargetTemperature": False,
+			"repetierStyleResends": False,
 			"okBeforeCommandOutput": False,
 			"smoothieTemperatureReporting": False,
 			"extendedSdFileList": False,