Make discovery persistent (#727)

* Make discovery persistent

* fix file handling

* fix detection

* Smooth

* Fix ring import

* Fix handling

* fix schema

* fix validate

* fix discovery cleanup

hassio/utils/validate.py

@@ -0,0 +1,28 @@
+"""Validate utils."""
+
+import pytz
+import voluptuous as vol
+
+
+def schema_or(schema):
+    """Allow schema or empty."""
+    def _wrapper(value):
+        """Wrapper for validator."""
+        if not value:
+            return value
+        return schema(value)
+
+    return _wrapper
+
+
+def validate_timezone(timezone):
+    """Validate voluptuous timezone."""
+    try:
+        pytz.timezone(timezone)
+    except pytz.exceptions.UnknownTimeZoneError:
+        raise vol.Invalid(
+            "Invalid time zone passed in. Valid options can be found here: "
+            "http://en.wikipedia.org/wiki/List_of_tz_database_time_zones") \
+                from None
+
+    return timezone