I have a primary python project that has a dependency of another python lib which is a maturin wrapped rust crate. My 'readthedocs' script is failing on the lib using maturin with: Caused by: lock file version `4` was found, but this version of Cargo does not understand this lock file, perhaps Cargo needs to be updated? maturin failed Caused by: Cargo metadata failed. Does your crate compile with `cargo build`? Caused by: `cargo metadata` exited with an error: Error running maturin: Command '['maturin', 'pep517', 'write-dist-info', '--metadata-directory', '/tmp/pip-modern-metadata-bginyxp6', '--interpreter', '/home/docs/checkouts/readthedocs.org/user_builds/pysui/envs/latest/bin/python']' returned non-zero exit status 1. Checking for Rust toolchain.... Running `maturin pep517 write-dist-info --metadata-directory /tmp/pip-modern-metadata-bginyxp6 --interpreter /home/docs/checkouts/readthedocs.org/user_builds/pysui/envs/latest/bin/python` [end of output] Is this a known issue, I could find nothing specific that describes a cure. Continue reading...