lxml 4.2.0 fails on pypy with "undefined symbol: PyFrozenSet_New"

[Marius Gedminas]

I have daily builds for zodbbrowser enabled on Travis CI. This has detected a new failure within the last couple of days:

Traceback (most recent call last):
  File "/home/travis/build/mgedmin/zodbbrowser/src/zodbbrowser/ftests/test_standalone.py", line 15, in <module>
    from lxml.html import fromstring, tostring
  File "/home/travis/virtualenv/pypy2.7-5.8.0/site-packages/lxml/html/__init__.py", line 54, in <module>
    from .. import etree
ImportError: unable to load extension module '/home/travis/virtualenv/pypy2.7-5.8.0/site-packages/lxml/etree.pypy-41.so': /home/travis/virtualenv/pypy2.7-5.8.0/site-packages/lxml/etree.pypy-41.so: undefined symbol: PyFrozenSet_New

The main differing variable is that this happens with lxml 4.2.0. The last successful build was using lxml 4.1.0.

I see this failure both on pypy2 and pypy3. Travis ships PyPy 5.8.0.

Link to failing Travis job:
- https://travis-ci.org/mgedmin/zodbbrowser/jobs/354249147

Link to last successful Travis job:
- https://travis-ci.org/mgedmin/zodbbrowser/jobs/352260202

[scoder (scoder)]

That's a bug in Cython, fixed here:
https://github.com/cython/cython/commit/96d76b4c37a1cbec54bcc8bd2d652cd47add0681
I'll use Cython 0.28.1 for the next bug fix release, as soon as it's out.
As a work-around, you can rebuild lxml with Cython 0.27.x.