Comment 3 for bug 1783252

16.04 is now in maintenance and any SRUs need to be carefully considered for potential regressions. Also, the impact of toolchain regressions can be far reaching.

As greenlet 0.4.14 is not supported on 16.04, and there are newer LTS versions of Ubuntu available which are unaffected by this issue, we are marking this as "Won't fix".
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Since the self-recompiled version 0.4.14 of python-greenlet is newer than the one from the archive::
$ rmadison --arch=ppc64el python-greenlet | grep xenial
 python-greenlet | 0.4.9-2fakesync1 | xenial | ppc64el
it won’t be supported anyway.
Hence one may also just consider an (unsupported but as-is available) compiler from the
“Toolchain test builds” PPA:
https://launchpad.net/~ubuntu-toolchain-r/+archive/ubuntu/test
It has a newer gcc-5 version compared to the one in xenial / main (but I think is still not working):
gcc-5 5.5.0-12ubuntu1~16.04
But there are also even more recent gcc versions 6, 7 and 8 for xenial:
gcc-6 6.4.0-17ubuntu1~16.04
gcc-7 7.3.0-21ubuntu1~16.04
gcc-8 8.1.0-5ubuntu1~16.04