URLs in encoded form can be used for import:
https://ar.wikipedia.org/wiki/%D9%85%D9%84%D9%81:1967%2BTUN.jpg
https://ar.wikipedia.org/wiki/%D9%85%D9%84%D9%81:UD_%D9%84%D9%88%D8%BA%D8%B1%D9%8A%D9%86%D9%8A%D9%8A%D8%B3.png
Unencoded URLs can't:
`https://ar.wikipedia.org/wiki/ملف:1967+TUN.jpg`
`https://ar.wikipedia.org/wiki/File:UD لوغرينييس.png`
```counterexample
Failed to discover API location from: "https://ar.wikipedia.org/wiki/File:UD لوغرينييس.png". Status code 200,
```
Technically this is a missing feature, but from the users perspective (these users are used to unencoded URLs working) it's a bug.
Acceptance criteria:
[x] Accept unencoded URLs with plus signs. https://gerrit.wikimedia.org/r/437729
[x] Accept unencoded URLs with spaces. https://gerrit.wikimedia.org/r/437435
[x] Also note the dangling comma at the end of the message. This should be fixed as well. https://gerrit.wikimedia.org/r/437478