Added a general comment describing jsonurl.py and updated the error
handling of recursive key lookup to avoid printing the Python "stack
trace" when there is an exception (i.e., more becoming of a utility).

Review: https://reviews.apache.org/r/9376

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1448446 13f79535-47bb-0310-9956-ffa450edef68
Added stout Error and None (w/ tests).

Review: https://reviews.apache.org/r/9304

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1448464 13f79535-47bb-0310-9956-ffa450edef68
Minor cleanups in src/logging.cpp.

Review: https://reviews.apache.org/r/9305

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1448465 13f79535-47bb-0310-9956-ffa450edef68
Refactored all Try<T>::error and Result<T>::error to use Error or
ErrnoError (also changed a few CHECKs into CHECK_SOMEs).

Review: https://reviews.apache.org/r/9306

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1448466 13f79535-47bb-0310-9956-ffa450edef68
Refactored all Option<T>::none and Result<T>::none to use None.

Review: https://reviews.apache.org/r/9307

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1448467 13f79535-47bb-0310-9956-ffa450edef68
Added Future::then which takes result of defer.

Review: https://reviews.apache.org/r/9569

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1449438 13f79535-47bb-0310-9956-ffa450edef68
Simplified Future::then(_Bind) implementations.

Review: https://reviews.apache.org/r/9570

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1449439 13f79535-47bb-0310-9956-ffa450edef68
Renamed 'deferred' to 'Deferred'.

Review: https://reviews.apache.org/r/9571

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1449440 13f79535-47bb-0310-9956-ffa450edef68