hgext/convert/cvs.py

--- a/hgext/convert/cvs.py	Thu Jan 12 19:59:01 2023 +0400
+++ b/hgext/convert/cvs.py	Fri Jan 13 00:56:37 2023 +0400
@@ -199,7 +199,7 @@
                 if sck.recv(128) != b"I LOVE YOU\n":
                     raise error.Abort(_(b"CVS pserver authentication failed"))
 
-                self.writep = self.readp = sck.makefile(b'r+')
+                self.writep = self.readp = sck.makefile('rwb')
 
         if not conntype and root.startswith(b":local:"):
             conntype = b"local"