- LP #397861: exporting $PYTHON in generated 'zopectl' for fixing import issue
  with "bin/zopectl adduser"

Revert r101557 and put back version pins for zodbcode and zope.app.interface. These are actual dependencies of zope.app.zcmlfiles, which in turn is a test dependency of numerous packages we use. Having a consistent known set of packages for tests is as important as having one for production.

- removed special PluginIndexes handling in Product initialization code

- added more XXX comments to the regression tests (don't know how to run and fix them)

Another round of package updates. These are no direct Zope2 dependencies, but required to run all tests of all direct dependencies

Added an allpy interpreter that has the same egg set as the alltests script. Changed the checknew script to check all packages found on sys.path, instead of only direct dependencies of Zope2. Otherwise we'll miss out on new releases from the test-only dependencies

- added XXX comments to the regression tests (don't know how to run and fix them)