Try telling who is/are requesting missing package

[davidlatwe]

So this is anothre shot after #971, which only focusing on missing package info this time.

Here is my test cases, and the output would be as follows:

Required package not found
====================
package family not found: oops, was required by: dummy (searched: memory@any)

Required package not found (deeper)
====================
package family not found: oops, was required by: dummy (searched: memory@any)

Required package not found (multiple)
====================
package family not found: oops, was required by: dummy, jojo (searched: memory@any)