rejoin format string

Author: Vladimir Kotal

tools/src/main/python/opengrok_tools/mirror.py

@@ -139,8 +139,8 @@ def main():
 
     nomirror = os.environ.get(OPENGROK_NO_MIRROR_ENV)
     if nomirror and len(nomirror) > 0:
-        logger.debug("skipping mirror based on the {} " +
-                     "environment variable".format(OPENGROK_NO_MIRROR_ENV))
+        logger.debug("skipping mirror based on the {} environment variable".
+                     format(OPENGROK_NO_MIRROR_ENV))
         return SUCCESS_EXITVAL
 
     if len(args.project) > 0 and args.all: