Comment 3 for bug 911292

 The issue isn't what separator is used, but rather whether a pattern that
can handle missing values can be written to be applied to the keys.

The separator is important only in so far as the Nvra key is displayed to users
exactly as found in the index on some code paths, and so aesthetics kick in.

But all the implementation needs is a representation that is sfficiently predictable
that a pattern with optional values etc can be written.