* Catch DistributionNotFound when pycrypto is absent
On Solaris 11, module `pkg_resources` throws `DistributionNotFound` on import if `cryptography` is installed but `pycrypto` is not. This change causes that situation to be handled gracefully.
I'm not using Paramiko or Vault, so I my understanding is that I don't
need `pycrpto`. I could install `pycrypto` to make the error go away, but:
- The latest released version of `pycrypto` doesn't build cleanly on Solaris (https://github.com/dlitz/pycrypto/issues/184).
- Solaris includes an old version of GMP that triggers warnings every time Ansible runs (https://github.com/ansible/ansible/issues/6941). I notice that I can silence these warnings with `system_warnings` in `ansible.cfg`, but not installing `pycrypto` seems like a safer solution.
* Ignore only `pkg_resources.DistributionNotFound`, not other exceptions.
With some earlier changes, continuing to forward failed hosts on
to the iterator with each TQM run() call was causing plays with
max_fail_pct set to fail, as hosts which failed in previous plays
were counting those old failures against the % calculation.
Also changed the linear strategy's calculation to use the internal
failed list, rather than the iterator, as this now represents the
hosts failed during the current run only.
This change makes it so we know when it is safe to get rid of the module
(when we stop supporting python2.4) and makes it easier for us to find
code that is using the functions in there to update.
If needed, we'll create a pycompat26 and pycompat27 as well. These
files are for functions that are needed on that python version to write
portable code. So python-2.4 compatible modules may need code in
pycompat24, python26+ modules may need code in pycompat26, etc. If
a function is needed in multiple python versions, we should implement it
in an internal common file and use import to put it in the namespace for
each pycompatXY module.
As noted in the comment, the TQM may be used for more than one play. As such,
after creating the new PlayIterator object it is necessary to mark any failed
hosts from previous calls to run() as failed in the iterator, so they are
properly skipped during any future calls to run().
