[MacPorts] #57770: py-kaitaistruct: add py37 subport

[MacPorts]

#57770: py-kaitaistruct: add py37 subport
------------------------------+----------------------
  Reporter:  petrrr           |      Owner:  yan12125
      Type:  enhancement      |     Status:  closed
  Priority:  Normal           |  Milestone:
 Component:  ports            |    Version:
Resolution:  fixed            |   Keywords:
      Port:  py-kaitaistruct  |
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Comment (by yan12125):

 Thank! As a side note, upstream declares compatibility with Python 3.7
 since version 0.8 (https://github.com/kaitai-
 io/kaitai_struct_python_runtime/commit/278d7451e887e82528b327cf99b3b35bca65caec
 #diff-2eeaed663bd0d25b7e608891384b7298). I didn't actually test it as the
 test suite is too complicated to setup.

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Ticket URL: <https://trac.macports.org/ticket/57770#comment:2>
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