crecord: use raw string for regular expression \s emits a SyntaxWarning in Python 3.8. Use a raw string to avoid escaping the \. Differential Revision: https://phab.mercurial-scm.org/D5819

patch: properly escape \ in string literals Python 3.8 will emit a SyntaxWarning for str/bytes with invalid escapes. This commit addresses 4 occurrences where we had a bare \ in a str/bytes. Differential Revision: https://phab.mercurial-scm.org/D5818

global: make some docstrings raw strings Python 3.8 emits a SyntaxWarning when a str/bytes contains invalid \ escapes. Various docstrings in our code base contain invalid \ escapes. This commit turns those docstrings into raw strings. Differential Revision: https://phab.mercurial-scm.org/D5816

global: use raw strings for regular expressions with escapes Escape sequences like \w, \s, and \d are technically invalid in str/bytes. This became a deprecation warning in Python 3.6 (https://bugs.python.org/issue27364). Python 3.8 bumps it to a SyntaxWarning (https://bugs.python.org/issue32912), which is non-silent by default. This commit changes a number of regular expressions to use br'' so regular expression special sequences don't need \\ literals. This fixes roughly half of the SyntaxWarning we see in the code base with Python 3.8. Differential Revision: https://phab.mercurial-scm.org/D5815