'GET /api/tool_shed_repositories/shed_category
Display a list of repositories in the selected category.
:param tool_shed_url: the url of the toolshed to get repositories from
:param category_id: the category to get repositories from'

@expose_api
@web.require_admin
def shed_category(self, trans, **kwd):

    tool_shed_url = kwd.get('tool_shed_url', '')
    category_id = kwd.get('category_id', '')
    params = dict(installable=True)
    tool_shed_url = common_util.get_tool_shed_url_from_tool_shed_registry(trans.app, tool_shed_url)
    url = util.build_url(tool_shed_url, pathspec=['api', 'categories', category_id, 'repositories'], params=params)
    category = json.loads(util.url_get(url))
    return category
