Change use of global sys.stdout, sys.stdin os.environ to a hgrequest object. Note: also change hgrequest.write(str(thing)) to hgrequest.write(thing), people should make sure they write strings.

#!/bin/sh

hg init
echo a > a
hg add a
hg commit -m "test" -d "0 0"
hg history
hg tag -d "0 0" "bleah" 
hg history

echo foo >> .hgtags
hg tag -d "0 0" "bleah2" || echo "failed"