Bug#896401: python3-seaborn: seaborn fails to import

[Helmut Grohne]

Package: python3-seaborn
Version: 0.8.0-1
Severity: serious
User: helmutg at debian.org
Usertags: python-import

After installing python3-seaborn importing the module seaborn
into a python interpreter fails with the following error:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3/dist-packages/seaborn/__init__.py", line 6, in <module>
    from .rcmod import *
  File "/usr/lib/python3/dist-packages/seaborn/rcmod.py", line 8, in <module>
    from . import palettes, _orig_rc_params
  File "/usr/lib/python3/dist-packages/seaborn/palettes.py", line 12, in <module>
    from .utils import desaturate, set_hls_values, get_color_cycle
  File "/usr/lib/python3/dist-packages/seaborn/utils.py", line 12, in <module>
    import matplotlib.pyplot as plt
  File "/usr/lib/python3/dist-packages/matplotlib/pyplot.py", line 115, in <module>
    _backend_mod, new_figure_manager, draw_if_interactive, _show = pylab_setup()
  File "/usr/lib/python3/dist-packages/matplotlib/backends/__init__.py", line 62, in pylab_setup
    [backend_name], 0)
  File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_tkagg.py", line 4, in <module>
    from . import tkagg  # Paint image to Tk photo blitter extension.
  File "/usr/lib/python3/dist-packages/matplotlib/backends/tkagg.py", line 5, in <module>
    from six.moves import tkinter as Tk
  File "/usr/lib/python3/dist-packages/six.py", line 92, in __get__
    result = self._resolve()
  File "/usr/lib/python3/dist-packages/six.py", line 115, in _resolve
    return _import_module(self.mod)
  File "/usr/lib/python3/dist-packages/six.py", line 82, in _import_module
    __import__(name)
ModuleNotFoundError: No module named 'tkinter'

The vast majority of import failures is attributed to missing dependencies.
Often times that manifests as an ImportError or ModuleNotFoundError.
Typically, dependencies should be inserted by dh-python via ${python:Depends}
or ${python3:Depends}. Thus a missing dependency can be caused by incomplete
install_requires in setup.py. Sometimes a missing dependency of a dependency
is the cause, in such cases this bug should be reassigned.

Helmut