Verbose errors.

Author: Julian

bin/jsonschema_suite

@@ -1,15 +1,32 @@
 #! /usr/bin/env python
-import argparse
+import sys
+import textwrap
+
+try:
+    import argparse
+except ImportError:
+    print textwrap.dedent("""
+        The argparse library could not be imported. jsonschema_suite requires
+        either Python 2.7 or for you to install argparse. You can do so by
+        running `pip install argparse`, `easy_install argparse` or by
+        downloading argparse and running `python2.6 setup.py install`.
+
+        See https://pypi.python.org/pypi/argparse for details.
+    """.strip("\n"))
+    sys.exit(1)
+
 import errno
 import fnmatch
 import json
 import os
 import random
 import shutil
-import sys
 import unittest
 import warnings
 
+if getattr(unittest, "skipIf", None) is None:
+    unittest.skipIf = lambda cond, msg : lambda fn : fn
+
 try:
     import jsonschema
 except ImportError:
@@ -109,7 +126,7 @@ class SanityTests(unittest.TestCase):
 
     def test_all_descriptions_are_unique(self):
         for group in groups(self.test_files):
-            descriptions = {test["description"] for test in group["tests"]}
+            descriptions = set(test["description"] for test in group["tests"])
             self.assertEqual(
                 len(descriptions),
                 len(group["tests"]),
@@ -188,7 +205,15 @@ def main(arguments):
         try:
             from flask import Flask, jsonify
         except ImportError:
-            print "Flask is required to serve the test schemas. Aborting."
+            print textwrap.dedent("""
+                The Flask library is required to serve the remote schemas.
+
+                You can install it by running `pip install Flask`.
+
+                Alternatively, see the `jsonschema_suite remotes` or
+                `jsonschema_suite dump_remotes` commands to create static files
+                that can be served with your own web server.
+            """.strip("\n"))
             sys.exit(1)
 
         app = Flask(__name__)