Remove mkvenv-pypi-old

doc/install.asciidoc

@@ -424,10 +424,6 @@ https://docs.python.org/3/library/venv.html[virtual environment]:
 $ tox -e mkvenv-pypi
 ----
 
-If your system comes with Python 3.5.3 or older (such as Ubuntu 16.04 LTS), use
-`tox -e mkvenv-pypi-old` instead. This installs an older Qt version (5.10) due
-to bugs in newer versions.
-
 This installs all needed Python dependencies in a `.venv` subfolder.
 
 This comes with an up-to-date Qt/PyQt including QtWebEngine, but has a few

tox.ini

@@ -62,19 +62,6 @@ deps =
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/misc/requirements/requirements-pyqt.txt
 
-# Older PyQt for Python 3.5
-# 5.11.2: https://www.riverbankcomputing.com/pipermail/pyqt/2018-July/040511.html
-# 5.10.1: https://github.com/qutebrowser/qutebrowser/issues/3662
-[testenv:mkvenv-pypi-old]
-basepython = {env:PYTHON:python3.5}
-envdir = {toxinidir}/.venv
-commands = {envpython} -c ""
-usedevelop = true
-deps =
-    -r{toxinidir}/requirements.txt
-    PyQt5==5.10
-    sip==4.19.8
-
 [testenv:misc]
 ignore_errors = true
 basepython = {env:PYTHON:python3}