[3.9] bpo-40777: Initialize PyDateTime_IsoCalendarDateType.tp_base at run-time (GH-20493) #20495
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Recent changes to _datetimemodule broke compilation on mingw; see the comments in this change for details.
FWIW, @corona10: this issue is why
PyType_FromModuleAndSpec& friends take thebasesargument at run time.(cherry picked from commit 459acc5)
Co-authored-by: Petr Viktorin [email protected]
https://bugs.python.org/issue40777
Automerge-Triggered-By: @encukou