failure to handle connection errors

[Robert Collins]

bzr is not completely clear, to API users, about whether 'NotBranchError' is the only error they need to catch.

I think this is a bug in bzr, because, http can do smart server messages, and a connection reset from one http client (because the server doesn't support POST), doesn't meant that svn's http handler won't work.

This is also a bzr-svn issue, 'how to signal *I couldn't tell*' about a branch.

We should decide how to manage this in bzr (e.g. 'always raise a subclass of NotBranchError, use different subclasses for cases like 'ConnectionReset' or 'raise ProbeFailed(your_error)', and then we can fix this bug in pqm.

No handlers could be found for logger "bzr"
Permission denied (publickey).

Traceback (most recent call last):
  File "/home/pqm/pqm/bin/pqm", line 245, in <module>
    manager.run(script_queue)
...
  File "/home/pqm/pqm/pqm/script.py", line 612, in set_current_vcs
    branch_vcs = self.get_branch_handler(branch)
  File "/home/pqm/pqm/pqm/script.py", line 473, in get_branch_handler
    if handler.branch_exists(self.script.getSender(), branchspec):
  File "/home/pqm/pqm/pqm/__init__.py", line 377, in branch_exists
    branch = Branch.open(branchspec)
...
  File "/home/pqm/source/bzr.dev/bzrlib/smart/message.py", line 247, in
_read_more
    "(and try -Dhpss if further diagnosis is required)")
bzrlib.errors.ConnectionReset: Connection closed: please check
connectivity and permissions (and try -Dhpss if further diagnosis is
required)

[Martin Pool (mbp)]

I don't really understand this bug:

> bzr is not completely clear, to API users, about whether 'NotBranchError' is the only error they need to catch.

I don't see why they would think that is the only error we could raise.