[yocto] pseudo interaction issue

[Peter Seebach]

Oh, nevermind, I just realized:  We use antimagic as the implementation
goo for PSEUDO_DISABLED.

So a call to os.popen() from a program which has PSEUDO_DISABLED set is
going to think it's in antimagic mode.

And suddenly, the trick is revealed:

os.popen() is bypassing all the runqueue stuff which is trying to
ensure that the environment is in a valid state.  So if bitbake code
calls os.popen(), it may behave weirdly, for the same reason that any
other direct invocation of fork() or system() or whatnot would behave
weirdly -- because bitbake is running with pseudo in a strange state.

So I think the thing is:

Because bitbake is running with PSEUDO_DISABLED, any child process that
is not explicitly set to either enable or unload pseudo is going to be
running under pseudo, with PSEUDO_DISABLED.  And that means we need to
ensure that PSEUDO_PREFIX stays set, because we need that even when
pseudo is disabled.  (It's used during some of the initial setup
sanity checks.)

-s
-- 
Listen, get this.  Nobody with a good compiler needs to be justified.