Fix XenError

If the XML error description does not exist in the filesystem, XenError
tried to call Exception.__init__(self, ''), which is invalid, as self is
not inheriting from Exception.

Github: fixes #158

Signed-off-by: Mate Lakat <mate.lakat@citrix.com>

drivers/xs_errors.py

@@ -28,8 +28,7 @@ class XenError(object):
     def __init__(self, key, opterr=None):
         # Check the XML definition file exists
         if not os.path.exists(XML_DEFS):
-            print "No XML def file found"
-            raise Exception.__init__(self, '')
+            raise Exception("No XML def file found")
 
         # Read the definition list
         self._fromxml('SM-errorcodes')

tests/test_xs_errors.py

@@ -0,0 +1,29 @@
+import unittest
+
+import testlib
+
+import xs_errors
+
+
+class TestXenError(unittest.TestCase):
+    @testlib.with_context
+    def test_without_xml_defs(self, context):
+        raised_exception = None
+        try:
+            xs_errors.XenError('blah')
+        except Exception, e:
+            raised_exception = e
+
+        self.assertTrue("No XML def file found" in str(e))
+
+    @testlib.with_context
+    def test_xml_defs(self, context):
+        context.setup_error_codes()
+
+        raised_exception = None
+        try:
+            xs_errors.XenError('SRInUse')
+        except Exception, e:
+            raised_exception = e
+
+        self.assertTrue("The SR device is currently in use" in str(e))