encoding: avoid cyclic dependency around "parsers" in pure Python build 80f2b63dd83a brought "asciilower" and "import parsers" into "encoding.py". This works fine with "parsers" module in C implementation, but doesn't with one in pure Python implementation, because the latter causes cyclic dependency below and aborting execution: util => i18n => encoding => parsers => util This patch delays importing "parsers" module until it is really needed, to avoid cyclic dependency around "parsers" in pure Python build.