ROSBagException should call the base constructor

[lukehansen]

In python 2.7 there is a subtle bug with unpickling custom exceptions; this was fixed in 3.3, see https://bugs.python.org/issue1692335. As a workaround for 2.7 we can re-define these exceptions as below.

class ROSBagException(Exception):
    """
    Base class for exceptions in rosbag.
    """
    pass
 
class ROSBagFormatException(ROSBagException):
    """
    Exceptions for errors relating to the bag file format.
    """
    pass

class ROSBagUnindexedException(ROSBagException):
    """
    Exception for unindexed bags.
    """
    def __init__(self, *args):
        ROSBagException.__init__(self, 'Unindexed bag')

For context, I came across this issue when a ROSBagUnindexedException was raised in a multiprocessing.Pool.map thread. It throws the __init__ exception and hangs, as described here: https://lists.gt.net/python/bugs/1025933

[dirk-thomas]

Can you please provide a pull request with the proposed patch against the current default branch (lunar-devel). Thanks.

[lukehansen]

Sure, though it's not really a ros_comm bug and has been patched in python 3.3. PR is here: #1210