tests: alias ui as uimod in test-walkrepo

tests: alias ui as uimod in test-ui-config

tests: alias ui as uimod in test-context

tests: alias ui as uimod in test-ancestor

tests: sort import lines in tinyproxy.py

tests: sort import lines in failfilemerge.py

tests: sort import lines in dumbhttp.py This series is an attempt to enable import-checker.py for tests/**.py, but it turned out not easy. Since many tests have been ported to absolute_import without the coverage, import-checker.py reports a lot of errors right now. Should we enable import-checker.py without fixing all of them so that we won't get more errors?

chgserver: change random state after fork Before this patch, extensions expecting a different random state per command will break since the chg request handler will inherit a same random state from the parent daemon process. This patch addresses the issue by calling random.seed() after fork.

chg: make connect debug message less repetitive Before this patch, "connect to" debug message is printed repeatedly because a previous patch changed how the chg client decides the server is ready to be connected. This patch revises the places we print connect debug messages so they are less repetitive without losing useful information.

chgserver: use relative path at socket.bind Before this patch, if the server address is long, the server will fail to listen and throw the error: socket.error: AF_UNIX path too long It is because AF_UNIX path usually has a very short length limit (107 chars on common platforms, see sys/un.h). This patch addresses the issue by using relative path instead. Therefore the directory length does not matter. It helps run tests with chg using a long $TMPDIR.