Add kcidb-validate

Add a "kcidb-validate" tool to make it easier to validate the I/O data
without submitting it, exactly the way the submitting would.

kcidb/__init__.py

@@ -5,6 +5,7 @@
 import json
 import sys
 from datetime import datetime
+import jsonschema
 from google.cloud import bigquery
 from google.api_core.exceptions import BadRequest
 from kcidb import db_schema
@@ -212,3 +213,23 @@ def schema_main():
     parser = argparse.ArgumentParser(description=description)
     parser.parse_args()
     json.dump(io_schema.JSON, sys.stdout, indent=4, sort_keys=True)
+
+
+def validate_main():
+    """Execute the kcidb-validate command-line tool"""
+    description = 'kcidb-validate - Validate I/O JSON data'
+    parser = argparse.ArgumentParser(description=description)
+    parser.parse_args()
+
+    try:
+        data = json.load(sys.stdin)
+    except json.decoder.JSONDecodeError as err:
+        print(err, sys.stderr)
+        return 1
+
+    try:
+        io_schema.validate(data)
+    except jsonschema.exceptions.ValidationError as err:
+        print(err, sys.stderr)
+        return 2
+    return 0

setup.py

@@ -52,6 +52,7 @@
             "kcidb-init = kcidb:init_main",
             "kcidb-cleanup = kcidb:cleanup_main",
             "kcidb-schema = kcidb:schema_main",
+            "kcidb-validate = kcidb:validate_main",
             "kcidb-submit = kcidb:submit_main",
             "kcidb-query = kcidb:query_main",
         ]