Add a simple CLI tool

setup.py

@@ -45,4 +45,9 @@
         "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
     ],
+    entry_points={
+        "console_scripts": [
+            "swagger-spec-validator = swagger_spec_validator.cli:main",
+        ],
+    },
 )

swagger_spec_validator/cli.py

@@ -0,0 +1,58 @@
+# -*- coding: utf-8 -*-
+"""
+Swagger spec validator.
+"""
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+from __future__ import unicode_literals
+
+
+import argparse
+import sys
+
+from swagger_spec_validator.common import SwaggerValidationError
+from swagger_spec_validator.util import validate_spec_url
+
+
+def _extract_error_message(exc):
+    """
+    The validators return nested errors coming from common.wrap_exception, but
+    other errors like invalid URLs aren't nested. Try to
+    """
+    try:
+        return exc.args[1].args[0]
+    except IndexError:
+        pass
+
+    return exc.args[0]
+
+
+def main():
+    parser = argparse.ArgumentParser(description=__doc__)
+
+    parser.add_argument("url", type=str, help="URL of Swagger spec to validate")
+    parser.add_argument(
+        "-q",
+        "--quiet",
+        action="store_true",
+        help="No output if validation is successful",
+    )
+
+    args = parser.parse_args()
+
+    try:
+        validate_spec_url(args.url)
+    except SwaggerValidationError as exc:
+        error_message = _extract_error_message(exc)
+        print(error_message, file=sys.stderr)
+        return 1
+
+    if not args.quiet:
+        print("Validation successful!", file=sys.stderr)
+
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())