Merge ~mwhudson/curtin:newer-pylint into curtin:master

[Michael Hudson-Doyle]

Update pylint version in tox.ini

The currently specified version does not work with the typing module
from Python 3.9, thus causing spurious isses on impish.

[Dan Bungert (dbungert)]

review: Approve

[Server Team CI bot (server-team-bot)]

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review: Approve (continuous-integration)

diff --git a/tox.ini b/tox.ini
index 3e86c7a..a169f19 100644
--- a/tox.ini
+++ b/tox.ini
@@ -44,7 +44,7 @@ commands = {envpython} -m pyflakes {posargs:curtin/ tests/ tools/}
 basepython = python3
 sitepackages = true
 deps = {[testenv]deps}
-    pylint==2.6.0
+    pylint==2.12.2
     git+https://git.launchpad.net/simplestreams
 commands = {envpython} -m pylint --errors-only {posargs:curtin tests/vmtests}