Debugging in PyCharm with using Vagrant VM connection - cannot import name to_string

 I've encountered an issue where I cannot debug in PyCharm connecting through Vagrant to the VM. This has worked fine for projects up until now. The VM image was recently updated so I'm wondering if that has had an effect. I can run programs in "run" mode, just not debug mode. Here's the error I get

Traceback (most recent call last): 
File "/home/vagrant/.pycharm_helpers/pydev/pydevd.py", line 25, 
    in <module> from _pydevd_bundle import pydevd_vars 
File "/home/vagrant/.pycharm_helpers/pydev/_pydevd_bundle/pydevd_vars.py", line 21, 
    in <module> from _pydevd_bundle.pydevd_utils import to_string 
ImportError: cannot import name to_string

Here are the different commands used to run the programs - the first one is debug mode, the second is normal mode

ssh://vagrant@127.0.0.1:2222/usr/bin/python -u /home/vagrant/.pycharm_helpers/pydev/pydevd.py --multiproc --qt-support --client '0.0.0.0' --port 32807 --file /home/vagrant/.pycharm_helpers/pycharm/utrunner.py /vagrant/project/project_test.py::ProjectTest true 

ssh://vagrant@127.0.0.1:2222/usr/bin/python -u /home/vagrant/.pycharm_helpers/pycharm/utrunner.py /vagrant/project/project_test.py::ProjectTest true

Any ideas what why to_string is found in normal mode but not debug?

Is there a way to reset the pydevd.py file?  I've tried uninstalling and reinstalling without success.