Removes old exception and dead code from py lib.

Dead code related to an old exception that is not used anymore were
still present in error handler of webdriver.

Fixes #7134

Cr-Mirrored-From: https://chromium.googlesource.com/external/github.com/SeleniumHQ/selenium
Cr-Mirrored-Commit: e0dd6a807836bd7d30b8189f4017f60a1853fa29
2 files changed