[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
----------------------------+------------------------
  Reporter:  lpagani91      |      Owner:  reneeotten
      Type:  defect         |     Status:  assigned
  Priority:  Normal         |  Milestone:
 Component:  ports          |    Version:  2.6.2
Resolution:                 |   Keywords:
      Port:  py-matplotlib  |
----------------------------+------------------------

Comment (by reneeotten):

 what is the output of {{{port installed | grep matplotlib}}}? I suspect
 that you didn't install the {{{+tkinter}}} variant, in that case the TkAgg
 backend will not be available. Additionally, it appears there is a typo in
 your import statement; I'm pretty sure it should be
 {{{FigureCanvasTkAgg}}} (note the capital "A" in "Agg").

 So can you please do {{{sudo port install pyXY-matplotlib +tkinter}}},
 correct your import statement and try again? Let us know if that resolved
 your problem!

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Ticket URL: <https://trac.macports.org/ticket/60175#comment:4>
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