Use a realpath for the temporary build directory.

[zvezdan]

Some systems have /tmp symlinked which confuses custom builds, such as
numpy. This ensures that real path is passed and that such builds
resolve their paths correctly during build and install.

Added test for the change and also for the previous related fix: #707

---

This was migrated from #3079 to reparent it to the master
branch. Please see original pull request for any previous discussion.

[pfmoore]

This seems to have caused the pypy tests on master to fail. Most seem related to a temporary PyPI issue, but there's a Unicode error in there that seems to still be happening.

[dstufft]

Hmm, that's strange. The tests were passing on PyPy before this landed.

[pfmoore]

Yeah, may not be this change. I just had a failure from my latest PR, and when I checked, the builds on master had been failing since this one was committed - but that may be a coincidence.

[pfmoore]

I wonder - could a server used in the test be returning non-ASCII data? Can't see the error at the moment because I see you restarted the test.

[dstufft]

I didn't restart the test, I did merge something else though :)

It's totally possible something is returning non ASCII data.

[pfmoore]

Ah, OK. I'll look at the test again when it completes, and see if I can work out what's going on.

[zvezdan]

@pfmoore
This patch was made in September last year (see the original patch number above)
It had been rebased numerous times and never had issues with passing tests after each rebase.
It passed all the tests before the merge too.

Also, if you look at the code change, the patch is dealing with directories and only strings used in the newly added tests are the prefix/suffix for the temporary directory names. They are plain strings and will be treated correctly by Python 2 or 3.

Thank you for checking what else could cause the failures you're seeing.

[pfmoore]

@zvezdan It appears to have cleared itself up now (or @dstufft fixed it - I didn't get to it before it started working, anyway). Sorry if I gave the impression I thought your PR was faulty - I didn't mean to, I was more wondering if anyone else had noticed the failure after this went in and was looking into it.

Anyway, it's gone away now, so no problem :-)

[zvezdan]

@pfmoore
Thanks for checking. No need to apologize. Anyone's PR can be faulty (including mine) and it's important to check the changes that could potentially cause issues. This forced us all to look at those Travis errors and find the root cause -- that's always a good thing. :-)

Thanks again!