#1129 Fixed unexpected errors in slcli subnet create

[acamacho82]

Fixes #1129

I found an annoying error when no price is found:

$ slcli subnet create --v6 public 32 11223344 --test

An unexpected error has occured:
Traceback (most recent call last):
  File "/home/acamacho/Workspace/interpreters/python27/local/lib/python2.7/site-packages/SoftLayer-5.6.4-py2.7.egg/SoftLayer/CLI/core.py", line 182, in main
    cli.main(**kwargs)
  File "/home/acamacho/Workspace/interpreters/python27/local/lib/python2.7/site-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/home/acamacho/Workspace/interpreters/python27/local/lib/python2.7/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/acamacho/Workspace/interpreters/python27/local/lib/python2.7/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/acamacho/Workspace/interpreters/python27/local/lib/python2.7/site-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/acamacho/Workspace/interpreters/python27/local/lib/python2.7/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/home/acamacho/Workspace/interpreters/python27/local/lib/python2.7/site-packages/click/decorators.py", line 64, in new_func
    return ctx.invoke(f, obj, *args, **kwargs)
  File "/home/acamacho/Workspace/interpreters/python27/local/lib/python2.7/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/home/acamacho/Workspace/interpreters/python27/local/lib/python2.7/site-packages/SoftLayer-5.6.4-py2.7.egg/SoftLayer/CLI/subnet/create.py", line 46, in cli
    result = mgr.add_subnet(network, quantity=quantity, vlan_id=vlan_id, version=version, test_order=test)
  File "/home/acamacho/Workspace/interpreters/python27/local/lib/python2.7/site-packages/SoftLayer-5.6.4-py2.7.egg/SoftLayer/managers/network.py", line 154, in add_subnet
    raise TypeError('Invalid combination specified for ordering a'
TypeError: Invalid combination specified for ordering a subnet.

Feel free to report this error as it is likely a bug:
    https://github.com/softlayer/softlayer-python/issues
The following snippet should be able to reproduce the error

So I removed the TypeError in NetworkManager.add_subnet() and improved the error message which comes from the api

$ slcli subnet create --v6 public 32 11223344 --test

There is no price id for 32 public ipv6

[coveralls]

Coverage increased (+0.2%) to 91.967% when pulling 6d5b3f4 on acamacho82:issues1129 into cfab07e on softlayer:master.