Using poetry export to check that the lockfile is up-to-date seems slow

[DMRobertson]

If I read these GHA logs correctly we spend 36 seconds exporting requirements:

2022-08-21T22:31:44.5772425Z ##[group]Run poetry export --without-hashes | (! grep "The lock file is not up to date") || (echo pyproject.toml was updated without running \`poetry lock --no-update\`. && false)
2022-08-21T22:31:44.5773070Z �[36;1mpoetry export --without-hashes | (! grep "The lock file is not up to date") || (echo pyproject.toml was updated without running \`poetry lock --no-update\`. && false)�[0m
2022-08-21T22:31:44.5828102Z shell: /usr/bin/bash --noprofile --norc -e -o pipefail {0}
2022-08-21T22:31:44.5828382Z env:
2022-08-21T22:31:44.5828669Z   pythonLocation: /opt/hostedtoolcache/Python/3.10.6/x64
2022-08-21T22:31:44.5829028Z   LD_LIBRARY_PATH: /opt/hostedtoolcache/Python/3.10.6/x64/lib
2022-08-21T22:31:44.5829308Z ##[endgroup]
2022-08-21T22:32:20.8390032Z ##[group]Run poetry install --no-interaction --extras="all"

See if there's a quicker way to check that the lockfile is up-to-date. Poetry should just need to

• parse pyproject.toml
• compute checksum
• compare to checksum in lockfile

so we don't need to run any of its exporting logic.

[DMRobertson]

Need to re-examine this for poetry 1.2

[DMRobertson]

We tried poetry lock --check (#10) briefly on 1.2.0 and it seemed to have a similar speed on my machine to running the export.