Fix tox -e coverage-py39-twtrunk

[adiroiban]

Tox / pip fails to install / creates the virtual env for klein using Twisted trunk

Here is a build failure - https://github.com/twisted/klein/runs/2306282515#step:6:287

There are 2 issues with pip deps resolution

---

requests depending on older idna - https://github.com/psf/requests/issues/5710

With the released Twisted I see that the following deps are installed... see requests==2.15.1

attrs==20.3.0,Automat==20.2.0,cffi==1.14.5,characteristic==14.3.0,constantly==15.1.0,coverage==5.5,cryptography==3.4.7,hyperlink==21.0.0,hypothesis==6.2.0,idna==3.1,incremental==21.3.0,klein @ file:///home/adi/chevah/klein/.tox/.tmp/package/1/klein-20.6.0.zip,pkg-resources==0.0.0,pyasn1==0.4.8,pyasn1-modules==0.2.8,pycparser==2.20,PyHamcrest==2.0.2,pyOpenSSL==20.0.1,requests==2.15.1,service-identity==18.1.0,six==1.15.0,sortedcontainers==2.3.0,treq==21.1.0,Tubes==0.2.0,Twisted==21.2.0,Werkzeug==1.0.1,zope.interface==5.2.0

With trunk it goes crazy :)

---

twisted[tls] --- I have no idea from where this is pulled

The user requested twisted 21.2.0.post0 (from https://github.com/twisted/twisted/archive/refs/heads/trunk.tar.gz)
    twisted[tls] 21.2.0 depends on twisted 21.2.0 (from https://files.pythonhosted.org/packages/f2/16/3eb9c66a7bfb5220c7bcbaaac33d359fe8a157b028959cd210983749b2e0/Twisted-21.2.0-py3-none-any.whl#sha256=aab38085ea6cda5b378b519a0ec99986874921ee8881318626b0a3414bb2631e (from https://pypi.org/simple/twisted/) (requires-python:>=3.5.4))

[adiroiban]

For request issue I have used

diff --git a/tox.ini b/tox.ini
index 48afb18..7a96018 100644
--- a/tox.ini
+++ b/tox.ini
@@ -39,6 +39,9 @@ deps =
     {test,coverage}: treq==21.1.0
     {test,coverage}: hypothesis==6.2.0
     {test,coverage}: idna==3.1
+    # Newer requests depend on older idna.
+    # See https://github.com/psf/requests/issues/5710
+    {test,coverage}: requests==2.15.1

[glyph]

It succeeds without --jobs, so something has changed in disttrial. I get this very suspicious error:

twisted.python.filepath.InsecurePath: '/Users/glyph/Projects/Klein/.tox/coverage-py39-twtrunk/log/trial.log' contains one or more directory separators

[glyph]

(Specifically after ^C)

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This is the bug: https://github.com/twisted/twisted/issues/11580