“With book and lyrics by Python co-founder Eric Idle and music by Idle and composer John Du Prez, “Spamalot” hits and misses for much of its first act but ultimately makes it home on sheer comic goodwill. It’s nice to be in the hands of comic professionals, and “Spamalot” has a few. I liked it, even when it seemed to be the work of a bunch of highly talented Python fans re-enacting scenes from a cherished film and making up some highly variable songs to go with it.”