python.find_deps: On failure, show stdout and stderr output from Pip

It's nice to have some idea right away of what went wrong.

A common error is running the import tool on a system without the
patched version of Pip. This now produces the following sort of message:

    baserockimport/exts/python.find_deps: Failed to get runtime dependencies
    for numpy at checkouts/python_numpy-tarball/. Output from Pip:
      Usage:
        pip install [options] <requirement specifier>
    [package-index-options] ...
        pip install [options] -r <requirements file> [package-index-options]
    ...
        pip install [options] [-e] <vcs project url> ...
        pip install [options] [-e] <local project path> ...
        pip install [options] <archive url/path> ...

      no such option: --list-dependencies

Change-Id: I902920b46b29b1e2b18736b2ff2b5f4f4cdb42df

0 files changed, 0 insertions, 0 deletions