Bad assertion in PrimePGroup for direct products

[wilfwilson]

In lib/gprd.gi, the method for PrimePGroup for direct products of p-groups contains the following lines:

p := First (DirectProductInfo( D ).groups, G -> PrimePGroup (G) <> fail);
Assert (1, ForAll (DirectProductInfo( D ).groups, G -> PrimePGroup (G) in [fail, p]));

In the first line, p is defined to be a group; however the assertion is written as if p is instead the prime of that p-group. This leads to bad assertion failures:

Observed behaviour

gap> SetAssertionLevel(1);
gap> G := CyclicGroup(IsPcGroup, 5);;
gap> H := Range(IsomorphismPermGroup(G));
Group([ (1,2,3,4,5) ])
gap> PrimePGroup(H);
Error, Assertion failure in
  Assert( 1, ForAll( DirectProductInfo( D ).groups, function ( G )
        return PrimePGroup( G ) in [ fail, p ];
    end ) ); at /Users/Wilf/GAP/lib/gprd.gi:269 called from
<function "unknown">( <arguments> )

I'm working on this fix for this.