py3: read/write plain lock file in binary mode

A lock file shouldn't contain '\n', so this isn't a BC.

contrib/python3-whitelist

@@ -373,6 +373,7 b' test-subrepo-deep-nested-change.t'
 test-subrepo.t
 test-symlinks.t
 test-tag.t
+test-tags.t
 test-treemanifest.t
 test-unamend.t
 test-uncommit.t

mercurial/util.py

@@ -1685,7 +1685,8 b' def makelock(info, pathname):'
     except AttributeError: # no symlink in os
         pass
 
-    ld = os.open(pathname, os.O_CREAT | os.O_WRONLY | os.O_EXCL)
+    flags = os.O_CREAT | os.O_WRONLY | os.O_EXCL | getattr(os, 'O_BINARY', 0)
+    ld = os.open(pathname, flags)
     os.write(ld, info)
     os.close(ld)
 
@@ -1697,7 +1698,7 b' def readlock(pathname):'
             raise
     except AttributeError: # no symlink in os
         pass
-    fp = posixfile(pathname)
+    fp = posixfile(pathname, 'rb')
     r = fp.read()
     fp.close()
     return r