Issues with using python37

[John Klos <john%ziaspace.com@localhost>]

Try this:

Install devel/glib2, then install mailman, which in turn installs 
py27-expat.

Then run pkg_rolling-replace -u:

RR> Tsorting dependency graph
RR> Selecting glib2 (devel/glib2) as next package to replace
RR> Checking if glib2 has new depends...
RR> glib2 has the following new depends (need to re-tsort):
rr> [python37 py37-expat libtool-base gmake pkgconf]
RR> Tsorting dependency graph
pkg_info: can't find package `py37-expat'
*** Couldn't extract PKGPATH from installed package py37-expat
*** Please read the errors listed above, fix the problem,
*** then re-run pkg_rolling-replace to continue.

How do we escape this versioning hell?

John