Colourize tab name in its infobar

This is for faster learning the colour <-> tab association and to
see quickly in which tab you’re currently in.
6 jobs for feature/autocolor-tabs in 5 minutes and 10 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Lint
failed #28235
allowed to fail
mypyc

00:00:49

failed #28233
allowed to fail
pylint-latest

00:03:36

passed #28234
pylint-plugins

00:02:19

passed #28232
security-check

00:00:52

 
  Test
passed #28236
pytest-3.7

00:00:59

passed #28237
pytest-latest

00:01:33

 
Name Stage Failure
failed
pylint-latest Lint
poezio/windows/info_wins.py:239:57: E0602: Undefined variable 'contact' (undefined-variable)
************* Module poezio.core.core
poezio/core/core.py:1078:8: E1102: self.tabs.next is not callable (not-callable)
poezio/core/core.py:1084:8: E1102: self.tabs.prev is not callable (not-callable)
************* Module poezio.core.tabs
poezio/core/tabs.py:297:12: E1102: self.prev is not callable (not-callable)
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1
failed
mypyc Lint
poezio/plugin_e2ee.py:329: error: Unexpected keyword argument "passthrough" for "_encrypt" of "E2EEPlugin"
poezio/plugin_e2ee.py:374: error: Item "MucTab" of "Union[MucTab, DynamicConversationTab, StaticConversationTab, PrivateTab]" has no attribute "parent_muc"
poezio/plugin_e2ee.py:374: error: Item "DynamicConversationTab" of "Union[MucTab, DynamicConversationTab, StaticConversationTab, PrivateTab]" has no attribute "parent_muc"
poezio/plugin_e2ee.py:374: error: Item "StaticConversationTab" of "Union[MucTab, DynamicConversationTab, StaticConversationTab, PrivateTab]" has no attribute "parent_muc"
poezio/plugin_e2ee.py:389: note: "_encrypt" of "E2EEPlugin" defined here
poezio/plugin_e2ee.py:499: error: Incompatible return value type (got "Union[str, int, float, bool]", expected "str")
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1