error code 255 in Catalina

[Jeff_Forshaw]

I tried to open my pre-existing repo in SourceTree (running macOS Catalina) and get the error "hg status failed with code 255....repository requires features unknown to this Mercurial: sparserevlog". My version of Mercurial (hg --version) is vdersion 5.3.

The repo works find and can be managed fine from the command line (for years). My hope was to transition away from the command line.

Any ideas?

[Jeff_Forshaw]

Further to my original query, I note that my system version of mercurial is newer than the one embedded in mercurial. I attempted to "use system mercurial" (in the Python.framework directory) but sourcetree greyed out the executable........

[Jeff_Forshaw]

Well I managed to switch to the system version which was located at

mine is located at /opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/mercurial

However....I now get error code 255 again but this time with "failed to import extension hgext.hgflow....module has no attribute." 

Something of a can of worms it seems......

[Jeff_Forshaw]

I got things working - just about - I needed to uncheck hgsubversion and hgflow, whilst using system mercurial. Is there a more elegant solution that doesn't reduce functionality?