[i18n] Use redgettext over pygettext (#2023)

* [i18n] Use redgettext over pygettext

* Clear out autogenerated `messages.pot` files

* Remove redundant `regen_messages.py` files

* Refactor `generate_strings.py` to use redgettext

* Install redgettext in Travis Crowdin job

* Clean up some problematic usages of gettext function

* Reformat

* Replace generate_strings.py with Makefile argument

* Update to redgettext 2.1, use exclusion pattern

Signed-off-by: Toby Harradine <tobyharradine@gmail.com>

.travis.yml

@@ -55,9 +55,10 @@ jobs:
       - echo "deb https://artifacts.crowdin.com/repo/deb/ /" | sudo tee -a /etc/apt/sources.list
       - sudo apt-get update -qq
       - sudo apt-get install -y crowdin
+      - pip install redgettext==2.1
       deploy:
       - provider: script
-        script: python3 ./generate_strings.py
+        script: make gettext
         skip_cleanup: true
         on:
           repo: Cog-Creators/Red-DiscordBot