# HG changeset patch
# User Augie Fackler <augie@google.com>
# Date 2017-09-19 04:27:55
# Node ID 2bdd55abd56c72e14c56cd8c7be40beeda02195c
# Parent  047f2af8ceb0e3a381678f74ea5cbd7c57dcc6e8

bundle2: portably grab first byte of part name for letter check

diff --git a/mercurial/bundle2.py b/mercurial/bundle2.py
--- a/mercurial/bundle2.py
+++ b/mercurial/bundle2.py
@@ -615,7 +615,7 @@ class bundle20(object):
         """add a stream level parameter"""
         if not name:
             raise ValueError(r'empty parameter name')
-        if name[0] not in pycompat.bytestr(string.ascii_letters):
+        if name[0:1] not in pycompat.bytestr(string.ascii_letters):
             raise ValueError(r'non letter first character: %s' % name)
         self._params.append((name, value))