bors.cleanup repo initialization

[digama0]

$ mix bors.cleanup --months 1
Cleaning data older than 1 months
** (ArgumentError) errors were found at the given arguments:

  * 1st argument: no persistent term stored with this key

    (erts 12.2.1) :persistent_term.get(:db_repo)
    (bors 0.1.0) lib/application.ex:19: BorsNG.Application.fetch_repo/0
    (bors 0.1.0) lib/mix/bors.cleanup.ex:70: Mix.Tasks.Bors.Cleanup.repos/0
    (bors 0.1.0) lib/mix/bors.cleanup.ex:35: Mix.Tasks.Bors.Cleanup.run/1
    (mix 1.12.2) lib/mix/task.ex:394: anonymous fn/3 in Mix.Task.run_task/3
    (mix 1.12.2) lib/mix/cli.ex:84: Mix.CLI.run_task/2

It seems the issue is that

bors-ng/lib/mix/bors.cleanup.ex

Line 70 in f6dbe6e

def repos, do: [BorsNG.Application.fetch_repo()]

is called without calling set_repo() first.