```
docker build .
Wed Dec  2 17:33:13 UTC 2020
Errno::EAGAIN: Resource temporarily unavailable - Resource temporarily unavailable
  waitpid at org/jruby/RubyProcess.java:919
   system at org/jruby/RubyKernel.java:1691
   <main> at -e:1
The command '/bin/sh -c nix-shell shell.nix --command "jruby -Xnative.verbose -w -d --dev -e 'system \"date\"'"' returned a non-zero code: 1

```