cleanup: rename check-translation.py checker function - don't hide global var

cleanup: remove some unused / duplicate imports

cleanup: fix some list comprehension redefinitions of existing vars In all the remaining cases the comprehension variable is used for the same thing as a previous loop variable. This will mute some pyflakes "list comprehension redefines" warnings.

cleanup: avoid local vars shadowing imports This will mute some pyflakes "import ... shadowed by loop variable" warnings.

cleanup: avoid _ for local unused tmp variables - that is reserved for i18n _ is usually used for i18n markup but we also used it for I-don't-care variables. Instead, name don't-care variables in a slightly descriptive way but use the _ prefix to designate unused variable. This will mute some pyflakes "import '_' ... shadowed by loop variable" warnings.

cleanup: make sure we always access members of imported modules This will make sure we get import errors, even if demandimport is enabled. This will also mute some pyflakes 'imported but unused' warnings.