run-tests: make sure to check if pygments is installed before using it e80041832e introduced support to color the output of tests but used pygments without checking whether it's installed or not. That breaks test-run-tests.t for machines which don't have pygments installed. This patch conditionalize the color test in test-run-tests.t and also add a check to make sure pygments is installed before using that.

sparse: require [section] in sparse config files (BC) Previously, [include] was implicit and pattern lines before a [section] were added to includes. Because the format may change in the future and explicit behavior, well, more explicit, this commit changes the config parser to reject pattern lines that don't occur in a [section]. Differential Revision: https://phab.mercurial-scm.org/D96

sparse: use set for capturing profiles Order doesn't need to be preserved. A set is acceptable. Differential Revision: https://phab.mercurial-scm.org/D95

util: remove dead code which used to be for old python2 versions Differential Revision: https://phab.mercurial-scm.org/D107