Use patch.patch() when checking for patch availability.
The test is closer to what we want to know. It also makes sense when you deal with patched versions of patch() as most people do under win32.
#!/bin/sh
unset HGUSER
EMAIL="My Name <myname@example.com>"
export EMAIL
hg init test
cd test
touch asdf
hg add asdf
hg commit -d '1000000 0' -m commit-1
hg tip
unset EMAIL
echo 1234 > asdf
hg commit -d '1000000 0' -u "foo@bar.com" -m commit-1
hg tip
echo "[ui]" >> .hg/hgrc
echo "username = foobar <foo@bar.com>" >> .hg/hgrc
echo 12 > asdf
hg commit -d '1000000 0' -m commit-1
hg tip
echo 1 > asdf
hg commit -d '1000000 0' -u "foo@bar.com" -m commit-1
hg tip
echo 123 > asdf
echo "[ui]" > .hg/hgrc
echo "username = " >> .hg/hgrc
hg commit -d '1000000 0' -m commit-1
rm .hg/hgrc
hg commit -d '1000000 0' -m commit-1 2>&1 | sed -e "s/'[^']*'/user@host/"