Converting errors to string drops their stack trace, making it more
difficult to debug their actual reason. We can instead pass the error
objects as-is to console.warn/error, so that Firefox/Chrome devtools
will show both the stack trace of the console.warn/error call, and the
original stack trace of the error.
This commit also enables the `unicorn/no-console-spaces` ESLint rule,
which avoids accidental extra spaces when passing multiple parameters to
`console.*` methods.
202b26487f