fs: improve error message for invalid flag
Pull Request check-list
-
Does make -j8 test
(UNIX) orvcbuild test nosign
(Windows) pass with this change (including linting)? -
Is the commit message formatted according to [CONTRIBUTING.md][0]? -
If this change fixes a bug (or a performance problem), is a regression test (or a benchmark) included? -
Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
Affected core subsystem(s)
fs
Description of change
Flags on fs.open and others can be passed as strings or int. Previously, if passing anything other than string or int, the error message would only say that flags must be an int.