--- a/mercurial/hgweb/common.py	Fri Oct 12 20:03:29 2018 +0000
+++ b/mercurial/hgweb/common.py	Fri Oct 12 19:49:02 2018 +0200
@@ -183,7 +183,7 @@
     try:
         os.stat(path)
         ct = pycompat.sysbytes(
-            mimetypes.guess_type(pycompat.fsdecode(path))[0] or "text/plain")
+            mimetypes.guess_type(pycompat.fsdecode(path))[0] or r"text/plain")
         with open(path, 'rb') as fh:
             data = fh.read()