Allow copying text from MusicBrainz ID Locator Failure Message

[marknoble]

When the MusicBrainz ID Locator generates a failure message, it is displayed in a scrollable panel, but the text from this cannot readily be copied elsewhere for analysis or documentation.

I'd suggest allowing this text to be copied.

[yoshiask]

I don't believe I can change whether that text is selectable. I can look into either adding a "copy text" button or a custom dialog I have more control over.