Don't try to reinstall pip packages on every Puppet run

[mcandre]

Only install a pip package when it's missing.

[giavac]

FWIW, this gets my vote.

[CpuID]

In theory this should already be the case? There is an onlyif pip freeze hiding in there?

[giavac]

There is
unless => "${pip_env} freeze | grep -i -e ${grep_regex}",
but only when $ensure is 'present'.
If $ensure is 'latest', then the unless condition is omitted.
I think I see now how it works and, in the absence of a better way to check the version of the current latest candidate, it seems reasonable.

What about using the output of pip search though? That'll tell us whether the INSTALLED version is the same as the LATEST, and could trigger the installation with an unless cause.