I came across this exercise from section 1.3 in Hatcher's "Algebric topology".
Construct finite graphs $X_1$ and $X_2$ having a common finite-sheeted covering space $X_1 \cong X_2$ , but such that there is no space having both $X_1$ and $X_2$ as covering spaces.
I tried thinking on some pairs of graphs but each pair I thought of, whom had an homeomorphic covering space, seemed to "inherit" the covering space's properties in a sense that I could always find a space which is covered by both graphs.
any suggestions?