enable Flake checks

[peterbecich]

No description provided.

[peterbecich]

haskell-tls/hs-tls#470

[peterbecich]

nix flake build

DocTest error

ERROR  ] [ThreadId 339] <no location info>: error: [GHC-87110]
[ERROR  ] [ThreadId 339]     Could not load module ‘Distribution.Server.Util.Markdown’.
[ERROR  ] [ThreadId 339]     It is a member of the hidden package ‘hackage-server-0.5.1:lib-server’.
[ERROR  ] [ThreadId 339]     You can run ‘:set -package hackage-server’ to expose it.
[ERROR  ] [ThreadId 339]     (Note: this unloads all the modules in the current scope.)
[ERROR  ] [ThreadId 338] Could not import module: Distribution.Server.Util.Validators.Internal. This can be caused by a number of issues: 

[ERROR  ] [ThreadId 338]  1. A module found by GHC contained tests, but was not in 'exposed-modules'. If you want
[ERROR  ] [ThreadId 338]     to test non-exposed modules follow the instructions here:
[ERROR  ] [ThreadId 338]     https://github.com/martijnbastiaan/doctest-parallel#test-non-exposed-modules

[ERROR  ] [ThreadId 338]  2. For Cabal users: Cabal did not generate a GHC environment file. Either:
[ERROR  ] [ThreadId 338]    * Run with '--write-ghc-environment-files=always'
[ERROR  ] [ThreadId 338]    * Add 'write-ghc-environment-files: always' to your cabal.project

[ERROR  ] [ThreadId 338]  3. For Cabal users: Cabal did not generate a GHC environment file in time. This
[ERROR  ] [ThreadId 338]     can happen if you use 'cabal test' instead of 'cabal run doctests'. See
[ERROR  ] [ThreadId 338]     https://github.com/martijnbastiaan/doctest-parallel/issues/22.

[ERROR  ] [ThreadId 338]  4. The testsuite executable does not have a dependency on your project library. Please
[ERROR  ] [ThreadId 338]     add it to the 'build-depends' section of the testsuite executable.

Maybe #1197 and srid/haskell-flake#264 are both necessary

[peterbecich]

The error is still this, something about DocTests

[ERROR  ] [ThreadId 338] The original reason given by GHCi was:

[ERROR  ] [ThreadId 338] Error:
[ERROR  ] [ThreadId 338] 
[ERROR  ] [ThreadId 338] <no location info>: error:
[ERROR  ] [ThreadId 338]     Could not load module ‘Distribution.Server.Util.Validators.Internal’
[ERROR  ] [ThreadId 338]     It is a member of the hidden package ‘hackage-server-0.5.1:lib-server’.
[ERROR  ] [ThreadId 338]     You can run ‘:set -package hackage-server’ to expose it.
[ERROR  ] [ThreadId 338]     (Note: this unloads all the modules in the current scope.)
[ERROR  ] [ThreadId 339] Could not import module: Distribution.Server.Util.Markdown. This can be caused by a number of issues: 

[ERROR  ] [ThreadId 339]  1. A module found by GHC contained tests, but was not in 'exposed-modules'. If you want
[ERROR  ] [ThreadId 339]     to test non-exposed modules follow the instructions here:
[ERROR  ] [ThreadId 339]     https://github.com/martijnbastiaan/doctest-parallel#test-non-exposed-modules

[ERROR  ] [ThreadId 339]  2. For Cabal users: Cabal did not generate a GHC environment file. Either:
[ERROR  ] [ThreadId 339]    * Run with '--write-ghc-environment-files=always'
[ERROR  ] [ThreadId 339]    * Add 'write-ghc-environment-files: always' to your cabal.project

[ERROR  ] [ThreadId 339]  3. For Cabal users: Cabal did not generate a GHC environment file in time. This
[ERROR  ] [ThreadId 339]     can happen if you use 'cabal test' instead of 'cabal run doctests'. See
[ERROR  ] [ThreadId 339]     https://github.com/martijnbastiaan/doctest-parallel/issues/22.

[ERROR  ] [ThreadId 339]  4. The testsuite executable does not have a dependency on your project library. Please
[ERROR  ] [ThreadId 339]     add it to the 'build-depends' section of the testsuite executable.

[ERROR  ] [ThreadId 339] See the example project at https://github.com/martijnbastiaan/doctest-parallel/blob/main/example/README.md for more information.

[ERROR  ] [ThreadId 339] The original reason given by GHCi was: