Use binary string constant for concatenation.

Author: bertwesarg

git/refs/symbolic.py

@@ -313,7 +313,7 @@ def set_reference(self, ref, logmsg=None):
 
         lfd = LockedFD(fpath)
         fd = lfd.open(write=True, stream=True)
-        fd.write(write_value.encode('ascii') + '\n')
+        fd.write(write_value.encode('ascii') + b'\n')
         lfd.commit()
 
         # Adjust the reflog