[MacPorts] #60175: cannot import name '_tkagg' from 'matplotlib.backends' in python 2.7 and python 3.8

[MacPorts]

#60175: cannot import name '_tkagg' from 'matplotlib.backends' in python 2.7 and
python 3.8
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  Reporter:  lpagani91      |      Owner:  reneeotten
      Type:  defect         |     Status:  closed
  Priority:  Normal         |  Milestone:
 Component:  ports          |    Version:  2.6.2
Resolution:  worksforme     |   Keywords:
      Port:  py-matplotlib  |
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Comment (by reneeotten):

 Replying to [comment:5 lpagani91]:
 > OK, I thought installing pyXY-tkinter was the thing to do.
 > How could I know that I have to install matplotlib +tkinter instead ??

 Installing {{{pyXY-tkinter}}} is indeed one of the things that need to
 happen, besides setting the activating the backend {{{tkagg=True}}} in
 {{{setup.cfg}}}. You can do {{{port variant pyXY-matplotlib}}}, which will
 give you a (short) description of all variants and their purpose. In this
 case that said "tkinter: Enable TkAgg backend", that would likely have
 given you sufficient information about which variant to install.

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Ticket URL: <https://trac.macports.org/ticket/60175#comment:7>
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