vagrant: update vagrant image to buster from jessie I honestly have no idea if this works since I don't use vagrant, but looking around online suggests it should work fine. Differential Revision: https://phab.mercurial-scm.org/D7309

packaging: remove references to debian jessie Jessie is on life support at this point, so let's update the list of releases in the Makefiles. Differential Revision: https://phab.mercurial-scm.org/D7308

sqlitestore: remove superfluous r-prefixes on strings I did this file separately because it's a _ton_ of hits and it had some manual reformatting fallout as a result of black squeezing some expressions onto a single line. Differential Revision: https://phab.mercurial-scm.org/D7307

cleanup: remove pointless r-prefixes on single-quoted strings This is the promised second step on single-quoted strings. These had existed because our source transformer didn't turn r'' into b'', so we had tagged some strings as r-strings to get "native" strings on both Pythons. Now that the transformer is gone, we can dispense with this nonsense. Methodology: I ran hg locate 'set:added() or modified() or clean()' | egrep '.*\.py$' | xargs egrep --color=never -n -- \[\^b\]\[\^a-z\]r\'\[\^\'\\\\\]\*\'\[\^\'\ in an emacs grep-mode buffer, and then used a keyboard macro to iterate over the results and remove the r prefix as needed. # skip-blame removing unneeded r prefixes left over from Python 3 migration. Differential Revision: https://phab.mercurial-scm.org/D7306

rust-threads: force Rayon to respect the worker count in config As per the inline comment, this is a workaround because Rust code does not yet know how to read config files. Differential Revision: https://phab.mercurial-scm.org/D7310

phabricator: use context manager form of progress in uploadchunks Follow-up to 453079605242 / D7046. Differential Revision: https://phab.mercurial-scm.org/D7134