aurweb.l10n: Translate without side effects

The install method in Python’s gettext API aliases the translator’s
gettext method to an application-global _(). We don’t use that anywhere,
and it’s clear from aurweb’s Translator interface that we want to
translate a piece of text without affecting any global namespace.
Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

aurweb/l10n.py

@@ -15,5 +15,4 @@ class Translator:
             self._translator[lang] = gettext.translation("aurweb",
                                                          self._localedir,
                                                          languages=[lang])
-        self._translator[lang].install()
-        return _(s)  # _ is not defined, what is this?  # noqa: F821
+        return self._translator[lang].gettext(s)