[Distutils] Parallel installation of incompatible versions

[Daniel Holth]

>> Like with pkg_resources, developers are warned to only "require Gems"
>> on things that are *not* imported (preferably in the equivalent of
>> our
>> console_scripts wrappers). Otherwise you get an unwanted Gem
>> dependency if you ever tried to use the same gem outside of the gem
>> system.
>>
>
> I don't really know what you mean by this - could you please reword it?

There should be only one call to the linker, at the very top of
execution. Otherwise in this pseudo-language example you can't use
foobar without also using the requires system:

myscript:
requires(a, b, c)
import foobar
run()

foobar:
requires(c, d) # No!