Resolving dependencies...
cabal: Could not resolve dependencies:
trying: Cabal-1.20.0.2/installed-f63... (user goal)
next goal: json-extra (user goal)
rejecting: json-extra-0.1.0.1 (conflict: Cabal =>
base==4.7.0.1/installed-1a5..., json-extra => base>=4.6 && <4.7)
rejecting: json-extra-0.1.0.0 (global constraint requires ==0.1.0.1)
Backjump limit reached (change with --max-backjumps).

Note: when using a sandbox, all packages are required to have consistent
dependencies. Try reinstalling/unregistering the offending packages or
recreating the sandbox.