youcompleteme key error when using vim

Question

For a few days now I always getting the following error when pressing any key in vim:

Error detected while processing "function <SNR>53_OnCursorMovedNormalMode[5]..<SNR>53_OnFileReadyToParse":
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/share/vim-youcompleteme/python/ycm/youcompleteme.py", line 508, in HandleFileParseRequest
    self.NativeFiletypeCompletionUsable() ):
  File "/usr/share/vim-youcompleteme/python/ycm/youcompleteme.py", line 255, in NativeFiletypeCompletionUsable
    self.NativeFiletypeCompletionAvailable() )
  File "/usr/share/vim-youcompleteme/python/ycm/youcompleteme.py", line 250, in NativeFiletypeCompletionAvailable
    vimsupport.CurrentFiletypes() ] )
  File "/usr/share/vim-youcompleteme/python/ycm/youcompleteme.py", line 249, in <listcomp>
    return any( [ self.FiletypeCompleterExistsForFiletype( x ) for x in
  File "/usr/share/vim-youcompleteme/python/ycm/youcompleteme.py", line 240, in FiletypeCompleterExistsForFiletype
    exists_completer = SendCompleterAvailableRequest( filetype )
  File "/usr/share/vim-youcompleteme/python/ycm/client/completer_available_request.py", line 57, in SendCompleterAvailableRequest
    request.Start()
  File "/usr/share/vim-youcompleteme/python/ycm/client/completer_available_request.py", line 45, in Start
    'semantic_completion_available' )
  File "/usr/share/vim-youcompleteme/python/ycm/client/base_request.py", line 81, in PostDataToHandler
    timeout ) )
  File "/usr/share/vim-youcompleteme/python/ycm/client/base_request.py", line 174, in JsonFromFuture
    _ValidateResponseObject( response )
  File "/usr/share/vim-youcompleteme/python/ycm/client/base_request.py", line 203, in _ValidateResponseObject
    their_hmac = ToBytes( b64decode( response.headers[ _HMAC_HEADER ] ) )
  File "/usr/lib/python3/dist-packages/requests/structures.py", line 54, in __getitem__
    return self._store[key.lower()][1]
KeyError: 'x-ycm-hmac'

I'm using vim on Ubuntu 16.04 with the official vim-youcompleteme package.

There are questions with the same problem on stackoverflow here and here, unfortunately without answers.

Answer 1

I had a similar problem with the same KeyError (although I don't know the exact error because I was not able to get the full traceback that you did)

I managed to fix it by adding the zesty repo and installing a newer version of youcompleteme

# add zesty repo
echo deb http://archive.ubuntu.com/ubuntu/ zesty main restricted universe multiverse | sudo tee /etc/apt/sources.list.d/zesty.list
sudo apt update

# update only vim-youcompleteme
sudo apt install -y vim-youcompleteme

# remove new repository so there aren't 1000+ packages to upgrade
sudo rm /etc/apt/sources.list.d/zesty.list
sudo apt update