First commit of avro alert schema

First commit of the avro schema discussed in #263

.gitlab/avro_schema_validator.py

+#!/usr/bin/env python3
+"""
+Parse all Avro schema in this repository.
+
+Errors are output in the GNU error format
+<https://www.gnu.org/prep/standards/html_node/Errors.html>.
+
+Adapted from Leo Singer's CI scripts from TACH/GCN project.
+"""
+from json.decoder import JSONDecodeError
+from glob import iglob
+import sys
+
+from fastavro.schema import load_schema, SchemaParseException, UnknownType
+
+failed = False
+
+for filename in iglob('_static/*.avsc'):
+    try:
+        load_schema(filename)
+    except JSONDecodeError as e:
+        print(f'{filename}:{e.lineno}:{e.colno}: error: {e.msg}', file=sys.stderr)
+        failed = True
+    except SchemaParseException as e:
+        print(f'{filename}: error: {e.args[0]}', file=sys.stderr)
+        failed = True
+    except UnknownType as e:
+        print(f'{filename}: error: unknown type: {e.args[0]}', file=sys.stderr)
+        failed = True
+
+if failed:
+    sys.exit(1)