Python: increase minimal supported cffi version

[badboy]

I think this fixes test failures such as this one: https://app.circleci.com/pipelines/github/mozilla/glean/7162/workflows/33e489f9-56fa-4f0b-b2fa-c4bf03b52604/jobs/124598 (see #1507).

I ran it locally and saw this:

Traceback (most recent call last):
  File "/home/jer/src/mozilla/glean/glean-core/python/.venv3.8/lib64/python3.9/site-packages/glean_sdk-34.1.0-py3.9-linux-x86_64.egg/glean/_subprocess/_process_dispatcher_helper.py", line 36, in <module>
    success = func(*args)
  File "/home/jer/src/mozilla/glean/glean-core/python/.venv3.8/lib64/python3.9/site-packages/glean_sdk-34.1.0-py3.9-linux-x86_64.egg/glean/net/ping_upload_worker.py", line 152, in _process
    time.sleep(incoming_task.wait / 1000)
OverflowError: timestamp too large to convert to C _PyTime_t

Adding some logging it shows that incoming_task.wait is some huge value, likely because it reads the wrong bytes from memory because of the wrong encoding of an anonymous struct inside a union.

cffi 1.0.0 was released in 2015.
cffi 1.11.5 was released in 2018.
IMO it's a safe-bet to increase our minimum required version there.

[mdboom]

I assume you picked 1.11.5 to get this from the cffi changelog?

Issue #357: fix ffi.emit_python_code() which generated a buggy Python file if you are using a struct with an anonymous union field or vice-versa.

Makes sense to me. It doesn't look like cffi is vendored in m-c, but if it were, that should be updated also.

[badboy]

I assume you picked 1.11.5 to get this from the cffi changelog?

Issue #357: fix ffi.emit_python_code() which generated a buggy Python file if you are using a struct with an anonymous union field or vice-versa.

Makes sense to me. It doesn't look like cffi is vendored in m-c, but if it were, that should be updated also.

Yeah, I picked the first version which contained something about unions. I didn't confirm that it is THE thing, but the tests seem to pass so at least its no harm?

[badboy]

For visibility the commit message replicated here:

cffi 1.11.5 has a fix when using a struct with an anonymous union field.
Release changelog: cffi.readthedocs.io/en/latest/whatsnew.html#v1-11-5

Relevant part:

Issue #357: fix ffi.emit_python_code() which generated a buggy Python file if you are using a struct with an anonymous union field or vice-versa.

cffi 1.12.2 is the first one to actually support Python 3.8
Release changelog: cffi.readthedocs.io/en/latest/whatsnew.html#v1-12-2

Relevant part:

Added temporary workaround to compile on CPython 3.8.0a2.

cffi 1.13 is the first one NOT listed under "Older versions".
So I picked that for no other reason than "it's still visible in the overview":
cffi.readthedocs.io/en/latest/index.html