while downloading language pack (installer was at 85 %), installer crashed

Binary package hint: ubiquity

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When crashed, installer reported:
Traceback (most recent call last):
  File "/usr/lib/ubiquity/bin/ubiquity", line 185, in ?
    main()
  File "/usr/lib/ubiquity/bin/ubiquity", line 180, in main
    install(args[0])
  File "/usr/lib/ubiquity/bin/ubiquity", line 56, in install
    ret = wizard.run()
  File "/usr/lib/ubiquity/ubiquity/frontend/gtkui.py", line 310, in run
    self.process_step()
  File "/usr/lib/ubiquity/ubiquity/frontend/gtkui.py", line 879, in process_step
    self.progress_loop()
  File "/usr/lib/ubiquity/ubiquity/frontend/gtkui.py", line 654, in progress_loop
    raise RuntimeError, ("Install failed with exit code %s\n%s" %
RuntimeError: Install failed with exit code 1
Traceback (most recent call last):
  File "/usr/share/ubiquity/install.py", line 1448, in ?
    install.run()
  File "/usr/share/ubiquity/install.py", line 390, in run
    self.remove_extras()
  File "/usr/share/ubiquity/install.py", line 1385, in remove_extras
    self.do_remove(difference)
  File "/usr/share/ubiquity/install.py", line 1280, in do_remove
    assert cache._depcache.BrokenCount == 0
AssertionError
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