The error shows up on :Gundo and looks like this:
Error detected while processing function gundo#GundoShow[1]..<SNR>116_GundoShow[4]..<SNR>116_GundoOpen[31]..<SNR>116_GundoRenderPreview:
line 2:
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/home/mg/.vim/bundle/Gundo/autoload/gundo.py", line 474, in GundoRenderPreview
_output_preview_text(_generate_preview_diff(current, node_before, node_after))
File "/home/mg/.vim/bundle/Gundo/autoload/gundo.py", line 382, in _generate_preview_diff
before_time, after_time))
File "/usr/lib/python3.5/difflib.py", line 1177, in unified_diff
_check_types(a, b, fromfile, tofile, fromfiledate, tofiledate, lineterm)
File "/usr/lib/python3.5/difflib.py", line 1312, in _check_types
raise TypeError('all arguments must be str, not: %r' % (arg,))
TypeError: all arguments must be str, not: 46
The result of `difflib.unified_diff()` may contains newlines at the end of its
each line. It's suppressed in original Vim, but it's illegal in Neovim.
Since there is no good way to prevent `difflib` from appending newlines to the
results, `_output_preview_text()` function should sanitize it.
Thanks @michamos
Reference:
a5edc5f257/src/nvim/api/buffer.c (L215)https://github.com/sjl/gundo.vim/pull/30#issuecomment-170064637
Python 3.5 adds type-checking to difflib, which causes gundo to fail.
This fixes the issue by converting the arguments to strings.
See https://bugs.python.org/issue17445 for details
Instead of displaying hardcoded "j/k" for motion between undo states,
real keymaps are fetched from `g:gundo_map_move_older` and
`g:undo_map_move_never` variables.
