Py-trees

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* [blackboard] global ``Blackboard.clear()`` method

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* [blackboard] don't do any copying, just pass handles around, `239 <https://github.com/splintered-reality/py_trees/pull/239>`_
* [blackboard] client ``exists()`` method, `238 <https://github.com/splintered-reality/py_trees/pull/238>`_
* [blackboard] global ``Blackboard.set()`` method
* [blackboard] client ``Blackboard.unset()`` method, `239 <https://github.com/splintered-reality/py_trees/pull/239>`_

1.3.x (2019-10-03)
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**Breaking API**

* [decorators] updated ``EternalGuard`` to accommodate new blackboard variable tracking mechanisms
* [behaviours] blackboard behaviours decoupled - ``CheckBlackboardVariableExists``, ``WaitForBlackboardVariable``
* [behaviours] blackboard behaviours decoupled - ``CheckBlackboardVariableValue``, ``WaitForBlackboardVariableValue``
* [behaviours] blackboard behaviours dropped use of the largely redundant ``ClearingPolicy``
* [visitors] collapsed ``SnapshotVisitor`` and ``WindsOfChangeVisitor`` functionality, `228 <https://github.com/splintered-reality/py_trees/pull/228>`_

**New Features**

* [blackboard] read/write access configuration for clients on blackboard keys
* [blackboard] log the activity on the blackboard
* [display] dot graphs now have an option to display blackboard variables
* [display] unicode to console the entire blackboard key-value store
* [display] unicode to console the blackboard activity stream
* [visitors] new ``DisplaySnapshotVisitor`` to simplify collection/printing the tree to console, `228 <https://github.com/splintered-reality/py_trees/pull/228>`_

**Bugfixes**

* [infra] only require test html reports on circle ci builds (saves a dependency requirement), `229 <https://github.com/splintered-reality/py_trees/pull/229>`_

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* [trees] standalone ``setup()`` method with timer for use on unmanaged trees, `198 <https://github.com/splintered-reality/py_trees/pull/198>`_
* [examples] fix api in ``skeleton_tree.py``, `199 <https://github.com/splintered-reality/py_trees/pull/199>`_

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* [trees] bugfix KeyError on publication of missing keys, `118 <https://github.com/splintered-reality/py_trees_ros/pull/118>`_
* [utilities] a ros myargv stipper, a'la ROS1 style, until something is available upstream

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* [blackboards] sweeping changes to accomodate the new blackboards with tracking, `109 <https://github.com/splintered-reality/py_trees_ros/pull/109>`_
* [backend] ensure tree modifications are published with an updated timestamp, `100 <https://github.com/splintered-reality/py_trees_ros/pull/100>`_
* [behaviours] subscriber related behaviours now *require* qos_profile args, `104 <https://github.com/splintered-reality/py_trees_ros/pull/104>`_
* [trees] ros parameterisation of the setup timeout, `101 <https://github.com/splintered-reality/py_trees_ros/pull/101>`_
* [trees] make use of the new `DisplaySnapshotVisitor`, `102 <https://github.com/splintered-reality/py_trees_ros/pull/102>`_

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* [utilities] permit discovery of multiples with find_topics, `97 <https://github.com/splintered-reality/py_trees_ros/pull/97>`_