templater: replace Py3-only exception types by super-types available in Py2 As noted by @indygreg, `test-check-pyflakes.t` started failing on Py2 after my recent D8894, because that introduced catching of the Py3-only types `ModuleNotFoundError` and `FileNotFoundError`. Let's switch to less precise types that are also available in Py2. Differential Revision: https://phab.mercurial-scm.org/D8902

hgweb: enable reading styles from resources in frozen binaries All we need to do to read styles from resources is to pass the file-like object we get from `open_template()` on to `frommapfile()`. This takes the number of failing tests with PyOxidizer from 62 to 54. Differential Revision: https://phab.mercurial-scm.org/D8901