Lockfile_path is now mandatory when using email_reply feature

tracim/tracim/config/app_cfg.py

@@ -394,8 +394,12 @@ class CFG(object):
         ))
         self.EMAIL_REPLY_LOCKFILE_PATH = tg.config.get(
             'email.reply.lockfile_path',
-            '/tmp/tracim_email_fetcher.lock'
+            ''
         )
+        if not self.EMAIL_REPLY_LOCKFILE_PATH and self.EMAIL_REPLY_ACTIVATED:
+            raise Exception(
+                mandatory_msg.format('email.reply.lockfile_path')
+            )
 
         self.TRACKER_JS_PATH = tg.config.get(
             'js_tracker_path',