billing: Cast return value of _mock_stripe to CallableT.
billing: Cast return value of _mock_stripe to CallableT.

Without the cast mypy raises the following error:

Incompatible return value type (got "Callable[..., Any]",
expected "CallableT")

This is a known issue: https://github.com/python/mypy/issues/1927

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