Python 2 dependency problem: pyquery

[cyranix]

pyquery has dropped Python 2 support as of v1.4.3, but pdfquery has no upper bound on this dependency for its Python 2 build.

See https://pypi.org/project/pyquery/ and view release notes for v1.4.1.

Solution: Change requirements_py2.txt to set an upper bound on pyquery.

Workaround: Since this library appears to be unmaintained at present, if you have legacy Python 2 applications which need pdfquery, set pyquery==1.4.1 in your requirements, or fork this library and edit the aforementioned requirements file accordingly.