Error on doctest

[buttercrab]

I am developing a project.
When I tried doctest, an error came out:
error[1m: the option Z is only accepted on the nightly compiler

[xd009642]

That's because to keep the doctest executables around tarpaulin uses a nightly feature persist-doctests. This means doctest coverage is currently a nightly only feature.

Tracking issue in the rust compiler: rust-lang/rust#56925

[buttercrab]

Oh, I solved it. Thanks!