Same issue as #367, just re-opening because it seems discussion there isn't getting noticed.

Options like --index-url and --extra-index-url are honored when passed explicitly to pip-sync, but ignored when they're included in requirements.txt. So something like this:

# requirements.in
--extra-index-url https://my.private.index/
private-package==1.0.0

will compile successfully (via pip-compile requirements.in) to:

# requirements.txt
--extra-index-url https://my.private.index/
private-package==1.0.0

but then pip-sync requirements.txt will throw Could not find a version that satisfies the requirement private-package==1.0.0.

This can obviously be worked around with pip-sync --extra-index-url https://my.private.index/ requirements.txt, but pip-sync should be able to recognize the option automatically.