Our internationalization system can't handle variable lookups like this. It's fine to do
```python
_("my internationalized string")
```
but you can't do
```python
s = "my internationalized string"
_(s)
```
The reason is because we have an internationalization scraper than runs through all the files in our project looking for strings that are surrounded by `_(` and `)`, or `gettext(` and `)`. If it finds such a string, it adds it to the list of strings that will be sent to Transifex to be translated by our translation teams. Because this scraper is very dumb, it can't find strings that are bound to variables, only static strings surrounded by the gettext function. (To be clear, the gettext function runs just fine on variables, but the translation teams can't translate the string if it isn't scraped.)

You should put gettext calls around the places where you define the strings in `self.text_customization`, so that they will be scraped there.