Docker build fails with "The package location 'semantic-source' does not exist."

[evheny0]

Hi! docker build on master fails with the following error:

Step 15/20 : RUN cabal v2-update &&     cabal v2-configure --flags="release" &&     cabal v2-build semantic:exe:semantic
 ---> Running in c3a6938786d5
Config file path source is default config file.
Config file /root/.cabal/config not found.
Writing default configuration to /root/.cabal/config
When using configuration(s) from /build/cabal.project, the following errors occurred:
The package location 'semantic-source' does not exist.

The command '/bin/sh -c cabal v2-update &&     cabal v2-configure --flags="release" &&     cabal v2-build semantic:exe:semantic' returned a non-zero code: 1

[patrickt]

Hmm, this is very mysterious. It’s as though it’s ignoring cabal.project, which… it shouldn’t.

[targeter21]

semantic-source is listed in the .dockerignore, which means it's not included when copying the source in.