tests: collapse some more trivial if PYTHON3 blocks
This doesn't account for all of the references to PYTHON3. But it
accounts for the ones that are more trivial and don't entail logical
changes.
Differential Revision: https://phab.mercurial-scm.org/D12235
BasedOnStyle: LLVM
IndentWidth: 8
UseTab: ForIndentation
BreakBeforeBraces: Linux
AllowShortIfStatementsOnASingleLine: false
IndentCaseLabels: false
AllowShortBlocksOnASingleLine: false
AllowShortFunctionsOnASingleLine: false
IncludeCategories:
- Regex: '^<'
Priority: 1
- Regex: '^"'
Priority: 2