tox -e lint is broken on pip 19.1

[twisted-trac]

	@hawkowl reported
Trac ID	trac#9633
Type	defect
Created	2019-04-27 00:34:43Z

$ tox -r -e lint
lint recreate: /home/hawkowl/code/twisted/build/lint
lint installdeps: pyflakes, twistedchecker>=0.7.1, diff-cover==0.9.12, pycodestyle
lint develop-inst: /home/hawkowl/code/twisted
ERROR: invocation failed (exit code 1), logfile: /home/hawkowl/code/twisted/build/lint/log/lint-2.log
ERROR: actionid: lint
msg: developpkg
cmdargs: ['/home/hawkowl/code/twisted/build/lint/bin/pip', 'install', '-e', '/home/hawkowl/code/twisted']

Obtaining file:///home/hawkowl/code/twisted
ERROR: Error installing 'file:///home/hawkowl/code/twisted': editable mode is not supported for pyproject.toml-style projects. pip is processing this project as pyproject.toml-style because it has a pyproject.toml file. Since the project has a setup.py and the pyproject.toml has no "build-backend" key for the "build_system" value, you may pass --no-use-pep517 to opt out of pyproject.toml-style processing. See PEP 517 for details on pyproject.toml-style projects.

Searchable metadata

trac-id__9633 9633
type__defect defect
reporter__hawkowl hawkowl
priority__normal normal
milestone__None None
branch__ 
branch_author__ 
status__closed closed
resolution__fixed fixed
component__core core
keywords__None None
time__1556325283754553 1556325283754553
changetime__1556635336548656 1556635336548656
version__None None
owner__Mark_Williams__mrw_____ Mark Williams <mrw@...>

[twisted-trac]

	@markrwilliams set owner to @markrwilliams @markrwilliams set status to closed

In changeset 38fc89e

#!CommitTicketReference repository="" revision="38fc89e1e627f669f6c8671c9238d43736f64f70"
Merge pull request #1131 from twisted/9633-ugh-pip

[#9633] Attempt to fix the linting issues by not using an editable install

Author: hawkowl

Reviewers: markrwilliams

Fixes: ticket:9633