Merge pull request #86 from kragniz/directory-not-existing-error-message

Improve error message if cassettes dir does not exist

betamax/exceptions.py

@@ -4,3 +4,7 @@ def __init__(self, message):
 
     def __repr__(self):
         return 'BetamaxError("%s")' % self.message
+
+
+class MissingDirectoryError(BetamaxError):
+    pass

betamax/serializers/proxy.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 from .base import BaseSerializer
+from betamax.exceptions import MissingDirectoryError
 
 import os
 
@@ -27,6 +28,12 @@ def __init__(self, serializer, cassette_path, allow_serialization=False):
         self.cassette_path = cassette_path
 
     def _ensure_path_exists(self):
+        directory, _ = os.path.split(self.cassette_path)
+        if not (directory == '' or os.path.isdir(directory)):
+            raise MissingDirectoryError(
+                'Configured cassette directory \'{0}\' does not exist - try '
+                'creating it'.format(directory)
+                )
         if not os.path.exists(self.cassette_path):
             open(self.cassette_path, 'w+').close()