api to help clean up created paths when errors occir in recipe install
and update methods.

Made sure buildout exited with a non-zeo exit status when errors
occurred.

https://bugs.launchpad.net/zc.buildout/+bug/71353

Now use  system setuptools  if it is  available.  This can  also speed
bootstrapping,  since we  don't need  to download  setuptools  in more
cases.

https://bugs.launchpad.net/zc.buildout/+bug/105081.

packages that can't be found or that cause version conflicts.

packages that can't be found or that cause version conflicts.

Fixed a renormalizer to prevent spurious test failures,

packages that can't be found or that cause version conflicts.

Download caches didn't work on mac os x if directories in the download
cache path were symbolic links.

This led to a pretty major refactoring.

No commit message

It wasn't possible to give options on the command line for sections
not defined in a configuration file.

  to avoid database corruption when a user breaks out of a buildout
  with control-c.

- Don't save an installed database if there are no installed parts or
  develop egg links.

sections.

Treat DistutilsErrors as user errors.

- Added "logical tracebacks" that show functionally what the buildout
  was doing when an error occurs.  Don't show a Python traceback
  unless the -D option is used.

- Added a -D option that causes the buildout to print a traceback and
  start the pdb post-mortem debugger when an error occurs.

be specified in a versions section.

Changed the log format for picked versions.

This will allow a versions feature to be added without updating all
recipes initially.  Later, recipes that support custom versions will
be able to override the defaults by passing options.

- The easy_install module install and build functions now accept a
  versions argument that supplied to mapping from project name to
  version numbers.  This can be used to fix version numbers for
  required distributions and their depenencies.

When a version isn't fixed, using either a versions option or using
  a fixed version number in a requirement, then a debug log message is
  emitted indicating the version picked.  This is useful for setting
  versions options.

- Added a remove testing helper function that removes files or directories.

no longer causes voluminous setuptools output.  Uisng -vv and -vvv
now triggers extra setuptools output.

Improved a logging message.