cleanup: name unused variables using convention of leading _ This helps checker tools ... and readability for those who knows and follows the convention.

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.