coverage: Disable coverage checking for exceptions.py.
coverage: Disable coverage checking for exceptions.py.

We also take the opportunity to slightly improve the errors if
AbstractEnum ever gets used.

tommyip/zulip,synicalsyntax/zulip,synicalsyntax/zulip,punchagan/zulip,kou/zulip,kou/zulip,timabbott/zulip,punchagan/zulip,tommyip/zulip,rht/zulip,brainwane/zulip,dhcrzf/zulip,rishig/zulip,eeshangarg/zulip,zulip/zulip,showell/zulip,kou/zulip,tommyip/zulip,rishig/zulip,brainwane/zulip,showell/zulip,hackerkid/zulip,timabbott/zulip,rht/zulip,shubhamdhama/zulip,hackerkid/zulip,andersk/zulip,tommyip/zulip,hackerkid/zulip,rht/zulip,jackrzhang/zulip,timabbott/zulip,punchagan/zulip,kou/zulip,timabbott/zulip,timabbott/zulip,eeshangarg/zulip,kou/zulip,jackrzhang/zulip,zulip/zulip,brainwane/zulip,brainwane/zulip,rht/zulip,jackrzhang/zulip,kou/zulip,andersk/zulip,synicalsyntax/zulip,rishig/zulip,punchagan/zulip,hackerkid/zulip,rishig/zulip,tommyip/zulip,brainwane/zulip,andersk/zulip,shubhamdhama/zulip,timabbott/zulip,rht/zulip,eeshangarg/zulip,brainwane/zulip,andersk/zulip,punchagan/zulip,rishig/zulip,synicalsyntax/zulip,brainwane/zulip,andersk/zulip,tommyip/zulip,tommyip/zulip,jackrzhang/zulip,andersk/zulip,showell/zulip,zulip/zulip,eeshangarg/zulip,hackerkid/zulip,rht/zulip,zulip/zulip,kou/zulip,punchagan/zulip,shubhamdhama/zulip,jackrzhang/zulip,dhcrzf/zulip,synicalsyntax/zulip,rishig/zulip,shubhamdhama/zulip,showell/zulip,shubhamdhama/zulip,dhcrzf/zulip,shubhamdhama/zulip,eeshangarg/zulip,zulip/zulip,andersk/zulip,hackerkid/zulip,showell/zulip,eeshangarg/zulip,zulip/zulip,jackrzhang/zulip,shubhamdhama/zulip,timabbott/zulip,dhcrzf/zulip,rishig/zulip,punchagan/zulip,dhcrzf/zulip,eeshangarg/zulip,showell/zulip,zulip/zulip,hackerkid/zulip,synicalsyntax/zulip,rht/zulip,synicalsyntax/zulip,dhcrzf/zulip,jackrzhang/zulip,showell/zulip,dhcrzf/zulip