[cbimport] Cannot import to a bucket with a full stop when '--scope-collection-exp' is passed

What is the problem?
cbimport allows you to import data to a bucket with a full stop in it, e.g. "test.sync". However, if you also pass --scope-collection-exp it fails with

ERRO: Failed to import document 50: invalid collection string expected no more than three elements

which is from here. The obvious solution - escaping the dot with a backslash - does not work and instead gives:

JSON import failed: invalid collection string bucket name contains invalid characters

which is from here.

What is the solution?
We should handle escaping in the --bucket parameter and make it consistent