Install outside of source in custom directory fails.

[nejucomo]

According to InstallDetails:

The "make install" target is a wrapper around "setup.py install" that uses --single-version-externally-managed to bypass the extra checking that setuptools does. This allows "make install" and "make install PREFIX=/usr/local" to work the same way as traditional unix software (via GNU autoconf, etc).

This entire sequence of commands succeeds:

$ python ./setup.py build
$ python ./setup.py test # 0 unexpected errors
$ mkdir /usr/local/stow/allmydata-tahoe-1.4.1
$ make install PREFIX=/usr/local/stow/allmydata-tahoe-1.4.1/
$ cd /usr/local/stow
$ sudo stow allmydata-tahoe-1.4.1/
# cd ~; which tahoe

The output of which shows /usr/local/bin/tahoe as expected.

Yet some dependency or packaging issue is not configured correctly:

$ tahoe --help
Traceback (most recent call last):
  File "/usr/local/bin/tahoe", line 5, in <module>
    from pkg_resources import load_entry_point
  File "/usr/lib/python2.6/dist-packages/pkg_resources.py", line 2562, in <module>
    working_set.require(__requires__)
  File "/usr/lib/python2.6/dist-packages/pkg_resources.py", line 626, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/usr/lib/python2.6/dist-packages/pkg_resources.py", line 524, in resolve
    raise DistributionNotFound(req)  # XXX put more info here
pkg_resources.DistributionNotFound: allmydata-tahoe==1.4.1

This ticket is satisfied when this use case succeeds and the InstallDetails documentation specifies the proper procedure.