Error with ipdb and py.test: AttributeError: DontReadFromInput instance has no attribute 'encoding'

[blueyed]

I am seeing the following error with py.test when template_debug is included.

  File "venv/lib/python2.7/site-packages/template_debug/templatetags/debug_tags.py", line 8, in <module>
    import ipdb as pdb
  File "venv/lib/python2.7/site-packages/ipdb/__init__.py", line 16, in <module>
    from ipdb.__main__ import set_trace, post_mortem, pm, run, runcall, runeval, launch_ipdb_on_exception
  File "venv/lib/python2.7/site-packages/ipdb/__main__.py", line 51, in <module>
    ipshell = InteractiveShellEmbed()
  File "venv/lib/python2.7/site-packages/IPython/terminal/embed.py", line 92, in __init__
    display_banner=display_banner
  File "venv/lib/python2.7/site-packages/IPython/terminal/interactiveshell.py", line 328, in __init__
    **kwargs
  File "venv/lib/python2.7/site-packages/IPython/core/interactiveshell.py", line 483, in __init__
    self.init_readline()
  File "venv/lib/python2.7/site-packages/IPython/core/interactiveshell.py", line 1888, in init_readline
    self.refill_readline_hist()
  File "venv/lib/python2.7/site-packages/IPython/core/interactiveshell.py", line 1897, in refill_readline_hist
    stdin_encoding = sys.stdin.encoding or "utf-8"
AttributeError: DontReadFromInput instance has no attribute 'encoding'