Fix: Fixed broken unit test.

Unit test for mentat.script.fetcher was broken on machines, where mentat is not installed and /etc/metat/core directory does not exist. (Redmine issue: #1017)

lib/mentat/script/fetcher.py

@@ -174,7 +174,11 @@ class DemoFetcherScript(FetcherScript):
             # Override default configurations.
             #
             default_debug      = True,
-            default_config_dir = '/etc/mentat/core'
+            default_config_dir = os.path.abspath(
+                os.path.join(
+                    os.path.dirname(os.path.realpath(__file__)), '../../../conf/core'
+                )
+            )
         )
 
     def get_default_command(self):