diff between 'make build' and 'make mockbuild'

[Neal Becker]

I'm trying to debug why 'make build' of python-igraph-0.5.2-2 on fc12 gives 
segfault.  If I try to debug, using 'make mockbuild', I get a different 
result.  In that case, I get 
ERROR: Bad build req: No Package Found for igraph-devel = 0.5.2. Exiting.

Why does 'make build' find the required igraph-devel, but 'make mockbuild' 
doesn't, and what can I do about it?