[MacPorts] #60824: duplicity: Update to 0.8.14 and move dependencies to python 3.7

[MacPorts]

#60824: duplicity: Update to 0.8.14 and move dependencies to python 3.7
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  Reporter:  diekhans   |      Owner:  (none)
      Type:  update     |     Status:  new
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:
Resolution:             |   Keywords:
      Port:  duplicity  |
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Comment (by ryandesign):

 And unless duplicity is not compatible with it, we should move to the
 latest stable version of python, which is currently 3.8.

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Ticket URL: <https://trac.macports.org/ticket/60824#comment:3>
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