Fix validation of serial port on windows (#5749)

* Fix validation of serial port on windows

* Use pyserial to check serial ports.
* Check that persistence file ends with either `.json` or `.pickle`.

* Change fix to not rely on pyserial

* Use generator expr instead of list comprehension

homeassistant/components/mysensors.py

@@ -7,6 +7,7 @@ https://home-assistant.io/components/sensor.mysensors/
 import logging
 import os
 import socket
+import sys
 
 import voluptuous as vol
 
@@ -81,15 +82,37 @@ def has_all_unique_files(value):
     return value
 
 
+def is_persistence_file(value):
+    """Validate that persistence file path ends in either .pickle or .json."""
+    if value.endswith(('.json', '.pickle')):
+        return value
+    else:
+        raise vol.Invalid(
+            '{} does not end in either `.json` or `.pickle`'.format(value))
+
+
+def is_serial_port(value):
+    """Validate that value is a windows serial port or a unix device."""
+    if sys.platform.startswith('win'):
+        ports = ('COM{}'.format(idx + 1) for idx in range(256))
+        if value in ports:
+            return value
+        else:
+            raise vol.Invalid(
+                '{} is not a serial port'.format(value))
+    else:
+        return cv.isdevice(value)
+
+
 CONFIG_SCHEMA = vol.Schema({
     DOMAIN: vol.Schema({
         vol.Required(CONF_GATEWAYS): vol.All(
             cv.ensure_list, has_all_unique_files,
             [{
                 vol.Required(CONF_DEVICE):
-                    vol.Any(cv.isdevice, MQTT_COMPONENT, is_socket_address),
+                    vol.Any(MQTT_COMPONENT, is_socket_address, is_serial_port),
                 vol.Optional(CONF_PERSISTENCE_FILE):
-                    vol.All(cv.string, has_parent_dir),
+                    vol.All(cv.string, is_persistence_file, has_parent_dir),
                 vol.Optional(
                     CONF_BAUD_RATE,
                     default=DEFAULT_BAUD_RATE): cv.positive_int,