I just downloaded Inkscape on my Mac version 11.2.  I also downloaded the extension for Living Hinges.  When I attempted to try my first hinge I got an error which said : living_hinge.py:49: DeprecationWarning: Effect.OptionParser or `optparse` has been deprecated and replaced with `argparser`.You must change `self.OptionParser.add_option` to `self.arg_parser.add_argument`; the arguments are similar.
  self.OptionParser.add_option('--unit',action='store',type='string', dest='unit',default='mm',help='units of measurement')
living_hinge.py:50: DeprecationWarning: Effect.OptionParser or `optparse` has been deprecated and replaced with `argparser`.You must change `self.OptionParser.add_option` to `self.arg_parser.add_argument`; the arguments are similar.
  self.OptionParser.add_option('--cut_length',action='store',type='float', dest='cut_length',default=0,help='length of the cuts for the hinge.')
living_hinge.py:51: DeprecationWarning: Effect.OptionParser or `optparse` has been deprecated and replaced with `argparser`.You must change `self.OptionParser.add_option` to `self.arg_parser.add_argument`; the arguments are similar.
  self.OptionParser.add_option('--gap_length',action='store',type='float', dest='gap_length',default=0,help='separation distance between successive hinge cuts.')
living_hinge.py:52: DeprecationWarning: Effect.OptionParser or `optparse` has been deprecated and replaced with `argparser`.You must change `self.OptionParser.add_option` to `self.arg_parser.add_argument`; the arguments are similar.
  self.OptionParser.add_option('--sep_distance',action='store',type='float', dest='sep_distance',default=0,help='distance between successive lines of hinge cuts.')
living_hinge.py:180: DeprecationWarning: Effect.affect is now `Effect.run()`. The `output` argument has changed.
  effect.affect()
living_hinge.py:58: DeprecationWarning: Effect.unittouu is now a method in the svg document. Use `self.svg.unittouu(str)` instead.
  l = self.unittouu(str(self.options.cut_length) + unit)
living_hinge.py:60: DeprecationWarning: Effect.unittouu is now a method in the svg document. Use `self.svg.unittouu(str)` instead.
  d = self.unittouu(str(self.options.gap_length) + unit)
living_hinge.py:63: DeprecationWarning: Effect.unittouu is now a method in the svg document. Use `self.svg.unittouu(str)` instead.
  dd = self.unittouu(str(self.options.sep_distance) + unit)
living_hinge.py:66: DeprecationWarning: Effect.selected is now a dict in the svg. Use `self.svg.selected`.
  if self.selected:
living_hinge.py:68: DeprecationWarning: Effect.current_layer is now a method in the svg. Use `self.svg.get_current_layer()` instead.
  parent = self.current_layer
living_hinge.py:69: DeprecationWarning: Effect.selected is now a dict in the svg. Use `self.svg.selected`.
  for id, node in self.selected.iteritems():
Traceback (most recent call last):
  File "living_hinge.py", line 180, in <module>
    effect.affect()
  File "/Applications/Inkscape.app/Contents/Resources/share/inkscape/extensions/inkex/deprecated.py", line 181, in affect
    return self.run(args=args)
  File "/Applications/Inkscape.app/Contents/Resources/share/inkscape/extensions/inkex/base.py", line 140, in run
    self.save_raw(self.effect())
  File "living_hinge.py", line 69, in effect
    for id, node in self.selected.iteritems():
AttributeError: 'dict' object has no attribute 'iteritems'

I have no idea what this means, or what I need to do to fix it or if I even can......All I know is that a hinge did not appear in the box I created (can you tell I am very new to all of this?)

Any help would be very appreciated

Maybe you have seen this: https://inkscape.org/forums/questions/newbee-question/#c23905 .

I was unable to find this extension anywhere.  Would you be able to direct me further?

There is a button saying "attachments" in post #7 ,  the zip-file there can be downloaded, unpacked and the contents installed.

Oh thank you!.....Working on too small of a screen.  I will get down to big computer.  Very much appreciated!

I think it worked!