Atomic install

[mottosso]

Rez is currently able to resolve a package, prior to it having been completely installed. That's a bug.

[mottosso]

Turns out this happen during the final copy from temporary directory into the package repository. The install itself is fine, but the copy is a plain shutil.copytree which presumably copies in the order returned by os.listdir (alphabetical). The easy solution would be to just pop the package.py file, and append it to the list.

[mottosso]

The reason this was a problem in this case was because the final copy was really really slow, to a VPN running at ~10kb/sec. So the install went well, in under a second, but then the actual copy took about 10 minutes, during which time the package would appear broken.

[mottosso]

Use rez cp for this. Post-install of pip packages, convert it locally as well, and then finally rez cp the package onto the server. That way we'll piggyback on the safety and robustness built into the rez cp command.

Can currently be done manually.

rez env pipz -- install six
rez cp six --dest-path /server/packages