Fix the non-termination of OPAM when sometimes we install an arbitrary package, see 006293e1f8bfb317dab59308cabe4363c6b67675 .
Merge pull request #372 from tuong/master

Fix the non-termination of OPAM when sometimes we install an arbitrary package, see 006293e1f8bfb317dab59308cabe4363c6b67675 .