Add Strict Metaschema Validation (#1101)

Improve schema validation.

This adds strict validation of config module definitions at testing
time, with plumbing included for future runtime validation. This
eliminates a class of bugs resulting from schemas that have definitions
that are incorrect, but get interpreted by jsonschema as
"additionalProperties" that are therefore ignored.

- Add strict meta-schema for jsonschema unit test validation
- Separate schema from module metadata structure
- Improve type annotations for various functions and data types

Cleanup:
- Remove unused jsonschema "required" elements 
- Eliminate manual memoization in schema.py:get_schema(),
        reference module.__doc__ directly

2 files changed, 4 insertions, 10 deletions

diff --git a/cloudinit/cmd/clean.py b/cloudinit/cmd/clean.py
index 928a8eea..3502dd56 100644
--- a/cloudinit/cmd/clean.py
+++ b/cloudinit/cmd/clean.py
@@ -11,11 +11,9 @@ import sys
 
 from cloudinit.stages import Init
 from cloudinit.subp import (ProcessExecutionError, subp)
-from cloudinit.util import (del_dir, del_file, get_config_logfiles, is_link)
-
-
-def error(msg):
-    sys.stderr.write("ERROR: " + msg + "\n")
+from cloudinit.util import (
+    del_dir, del_file, get_config_logfiles, is_link, error
+)
 
 
 def get_parser(parser=None):
diff --git a/cloudinit/cmd/cloud_id.py b/cloudinit/cmd/cloud_id.py
index 97608921..0cdc9675 100755
--- a/cloudinit/cmd/cloud_id.py
+++ b/cloudinit/cmd/cloud_id.py
@@ -6,6 +6,7 @@ import argparse
 import json
 import sys
 
+from cloudinit.util import error
 from cloudinit.sources import (
     INSTANCE_JSON_FILE, METADATA_UNKNOWN, canonical_cloud_id)
 
@@ -40,11 +41,6 @@ def get_parser(parser=None):
     return parser
 
 
-def error(msg):
-    sys.stderr.write('ERROR: %s\n' % msg)
-    return 1
-
-
 def handle_args(name, args):
     """Handle calls to 'cloud-id' cli.