py3: don't run source transformer on hgext3rd (extensions) It's unclear why the source transformer runs on hgext3rd. It's been like that since it was introduced in 1c22400db72d (mercurial: implement a source transforming module loader on Python 3, 2016-07-04), and that commit didn't say anything about it (but it says that it doesn't have "support [...] for extensions"). I find that the current handling of hgext3rd just makes it harder to convert extensions to Python 3. It makes you convert a bunch of strings passed to getattr() and kwargs[] to r'' that could otherwise have been left alone. It's also really confusing that the source transformer runs when you import the extension as "extensions.foo=", but not as "extension.foo=/some/path". I suppose there is small number of (very simple) extensions that would have worked without this patch that would now be broken. It seems okay to me to break those. Differential Revision: https://phab.mercurial-scm.org/D6614