[Biopython] Dropping Python 3.4 support?

[Peter Cock]

Dear Biopythoneers,

I would like to drop Python 3.4 support in order to reduce
our continuous integration testing requirements.

We currently (as of Biopython 1.73) support Python 2.7
(until 2020), and Python 3.4, 3.5, 3.6, 3.7.

According to the Python website, Python 3.4 and 3.5 are
still getting security fixes, with the final release of Python 3.4
expected March 2019 in line with end-of-life 2019-03-16.

https://www.python.org/dev/peps/pep-0429/
https://devguide.python.org/#status-of-python-branches

Would dropping Python 3.4 support inconvenience any
Biopython users? Should we wait one more release
(i.e. Biopython 1.74, which we might aim to release in
March 2019?)

Thanks,

Peter