Some message types not discovered in Bazel build

[srmainwaring]

Some message types are not discovered when published using the Bazel build. This is not particular to Python, but also occurs for the C++ examples (so it does not appear to be a binding issue).

How to replicate

From terminal 1 run the C++ rover_publisher:

$ ./bazel-bin/python_ignition/rover_publisher
Publishing pose on topic [/pose], twist on topic [/twist]
Publishing pose on topic [/pose], twist on topic [/twist]
...

From terminal 2 run the C++ ign_topic_echo subscribing to /pose:

$ /bazel-bin/python_ignition/ign_topic_echo -t /pose 
header {
  stamp {
    sec: 4
    nsec: 513947250
  }
}
name: "base_link"
id: 9
position {
  x: 4.6053049700144255
  y: 1.9470917115432527
}
orientation {
  z: 0.19866933079506122
  w: 0.98006657784124163
}
...

From terminal 2 run the C++ ign_topic_echo subscribing to /twist:

$ /bazel-bin/python_ignition/ign_topic_echo -t /twist

In the second case no messages are displayed for the type ignition.msgs.Twist

---

Using the Python tools we can verify that both messages are published:

$ ./bazel-bin/python_ignition/python/ign_topic_list  
/pose
/twist

$ ./bazel-bin/python_ignition/python/ign_topic_info -t /pose
Publishers [Address, Message Type]:
  tcp://192.168.1.31:62260, ignition.msgs.Pose

$ ./bazel-bin/python_ignition/python/ign_topic_info -t /twist
Publishers [Address, Message Type]:
  tcp://192.168.1.31:62260, ignition.msgs.Twist

---

The issue is apparent with other messages types as can be seen by using the multi-message publisher:

From terminal 1:

$ ./bazel-bin/python_ignition/python/pub_all_msg_types

From terminal 2:

$ ./bazel-bin/python_ignition/python/ign_topic_list
/cmd_vel
/double
/double_v
/float
/float_v
/header
/pid
/pose
/publish
/quat
/subscribe
/time
/topic_info
/twist
/vector3d
/wrench

and then checking each topic in turn:

# working
$ ./bazel-bin/python_ignition/ign_topic_echo -t /double
header {
  stamp {
    sec: 15
    nsec: 21
  }
}
data: 10
...

# not working
$ ./bazel-bin/python_ignition/ign_topic_echo -t /double_v

The issue does not occur when running the examples built using the CMake build.