[3.15] Test that `ValueError` is raised when `vfsopen` is passed an invalid mode...

[3.15] Test that `ValueError` is raised when `vfsopen` is passed an invalid mode (GH-154008) (#154064)

Test that `ValueError` is raised when `vfsopen` is passed an invalid mode (GH-154008)

* ValueError with message test

* Remove white space

* Apply suggestions from code review

Change from double quotes to single quotes.

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(cherry picked from commit 9f5af278960a2f73a2e070de5141701e72675cf6)

Co-authored-by: Rayan <157278782+ravg998@users.noreply.github.com>
Co-authored-by: Tomas R. <tomas.roun8@gmail.com>