I'm hitting this on master after (roughly) autogen.sh; make; make bytecode.
```
$ out/bin/lilypond ~/lilypond-src/input/regression/other/display-lily-tests.ly
GNU LilyPond 2.25.7 (running Guile 2.2)
Processing
`/home/user/lilypond-src/input/regression/other/display-lily-tests.ly'
[...]
/home/user/lilypond-src/input/regression/other/display-lily-tests.ly:252:8:
error: Guile signaled an error for the expression beginning here
\test #
#[ \key e \minor #]
No applicable method for #<<generic> - (4)> in call (- 0 #<Pitch e >)
/home/user/lilypond-src/input/regression/other/display-lily-tests.ly:252:7:
error: wrong type for argument 2. Expecting pair, found #<unspecified>
\test ##[ \key e \minor #]
[…]
```
