Adds extension support with emphasis on ease of extension creation. Extensions
strongly conform to preexisting neutron commands (/neutron/v2_0/*). A sample
extension has been included (/neutron/v2_0/contrib/_fox_sockets.py). As it is
assumed that the sample extension will be packaged with the client, small
changes were required to include it with the unit tests.
It is also possible to install a module with a 'neutronclient.extension' entry-
point defined. More information on this can be found in the stevedore docs
under the section "Loading the Plugins". Extension discovery is modeled after
nova's module discovery but deviates strongly beyond that.
A conforming module, at a minimum:
* Will have a class that subclasses NeutronClientExtension to provide the
requisite version support, paths, and variable names for the client.
Example: neutronclient.neutron.v2_0.contrib._fox_sockets.FoxInSocket
* Will have at least one class that subclasses from the ClientExtension*
classes to provide the new functionality to the client
Example: neutronclient.neutron.v2_0.contrib._fox_sockets.FoxInSocketsList
* ClientExtension* subclasses must have a shell_command class variable if the
command is to be available to the CLI (shell.py)
Example: neutronclient.neutron.v2_0.contrib._fox_sockets.FoxInSocketsList
Provides client command extensions through new classes: NeutronClientExtension,
and ClientExtension<Action>.
The precedence of command loading are as follows:
* hard coded commands are loaded first
* contribued commands (those in /contrib)
* external commands (installed in the environment) are loaded last
Commands that have the same name will be overwritten by commands that are
loaded later. To greatly change the execution of a command for your particular
extension you only need to override the execute method.
Currently this extension support is limited to top-level resources. Parent/
child relationships may be added if desired.
Change-Id: I5b2fe530c90b5ce1243fc10341d6d434a1ecea7a
Implements: blueprint extensible-neutronclient