Released version does not work in OpenStack releases later than Ocata

[fghaas]

Attempting to install version 10.0.0, from PyPI, into a heat-engine instance using Pike and later breaks heat-engine:

2018-09-26 09:08:21.946 6347 ERROR heat.common.plugin_loader [-] Failed to import module heat.engine.plugins.f5_heat.resources.f5_sys_iappservice                                             
2018-09-26 09:08:21.947 6347 CRITICAL heat-engine [-] Unhandled error: ImportError: cannot import name _LE                                                                                    
2018-09-26 09:08:21.947 6347 ERROR heat-engine Traceback (most recent call last):                                                                                                             
2018-09-26 09:08:21.947 6347 ERROR heat-engine   File "/openstack/venvs/heat-16.0.19/bin/heat-engine", line 11, in <module>                                                                   
2018-09-26 09:08:21.947 6347 ERROR heat-engine     sys.exit(main())                                                                                                                           
2018-09-26 09:08:21.947 6347 ERROR heat-engine   File "/openstack/venvs/heat-16.0.19/lib/python2.7/site-packages/heat/cmd/engine.py", line 85, in main                                        
2018-09-26 09:08:21.947 6347 ERROR heat-engine     launcher = launch_engine()                                                                                                                 
2018-09-26 09:08:21.947 6347 ERROR heat-engine   File "/openstack/venvs/heat-16.0.19/lib/python2.7/site-packages/heat/cmd/engine.py", line 70, in launch_engine                               
2018-09-26 09:08:21.947 6347 ERROR heat-engine     srv = engine.EngineService(cfg.CONF.host, rpc_api.ENGINE_TOPIC)                                                                            
2018-09-26 09:08:21.947 6347 ERROR heat-engine   File "/openstack/venvs/heat-16.0.19/lib/python2.7/site-packages/heat/engine/service.py", line 317, in __init__                               
2018-09-26 09:08:21.947 6347 ERROR heat-engine     resources.initialise()                                                                                                                     
2018-09-26 09:08:21.947 6347 ERROR heat-engine   File "/openstack/venvs/heat-16.0.19/lib/python2.7/site-packages/heat/engine/resources/__init__.py", line 68, in initialise                   
2018-09-26 09:08:21.947 6347 ERROR heat-engine     _load_global_environment(global_env)                                                                                                       
2018-09-26 09:08:21.947 6347 ERROR heat-engine   File "/openstack/venvs/heat-16.0.19/lib/python2.7/site-packages/heat/engine/resources/__init__.py", line 74, in _load_global_environment     
2018-09-26 09:08:21.947 6347 ERROR heat-engine     _load_global_resources(env)                                                                                                                
2018-09-26 09:08:21.947 6347 ERROR heat-engine   File "/openstack/venvs/heat-16.0.19/lib/python2.7/site-packages/heat/engine/resources/__init__.py", line 87, in _load_global_resources       
2018-09-26 09:08:21.947 6347 ERROR heat-engine     manager = plugin_manager.PluginManager(__name__)                                                                                           
2018-09-26 09:08:21.947 6347 ERROR heat-engine   File "/openstack/venvs/heat-16.0.19/lib/python2.7/site-packages/heat/engine/plugin_manager.py", line 56, in __init__                         
2018-09-26 09:08:21.947 6347 ERROR heat-engine     self.modules = list(modules())                                                                                                             
2018-09-26 09:08:21.947 6347 ERROR heat-engine   File "/openstack/venvs/heat-16.0.19/lib/python2.7/site-packages/heat/common/plugin_loader.py", line 97, in load_modules                      
2018-09-26 09:08:21.947 6347 ERROR heat-engine     module = _import_module(importer, module_name, package)                                                                                    
2018-09-26 09:08:21.947 6347 ERROR heat-engine   File "/openstack/venvs/heat-16.0.19/lib/python2.7/site-packages/heat/common/plugin_loader.py", line 73, in _import_module                    
2018-09-26 09:08:21.947 6347 ERROR heat-engine     module = loader.load_module(module_name)                                                                                                   
2018-09-26 09:08:21.947 6347 ERROR heat-engine   File "/usr/lib/python2.7/pkgutil.py", line 246, in load_module                                                                               
2018-09-26 09:08:21.947 6347 ERROR heat-engine     mod = imp.load_module(fullname, self.file, self.filename, self.etc)                                                                        
2018-09-26 09:08:21.947 6347 ERROR heat-engine   File "/openstack/venvs/heat-16.0.19/lib/python2.7/site-packages/f5_heat/resources/f5_sys_iappservice.py", line 21, in <module>               
2018-09-26 09:08:21.947 6347 ERROR heat-engine     from heat.common.i18n import _LE                                                                                                           
2018-09-26 09:08:21.947 6347 ERROR heat-engine ImportError: cannot import name _LE  

The consequence of this is that heat-engine never starts, rendering Heat unusable.

from heat.common.i18n import _LE worked in Ocata, but was removed in Pike. See openstack/heat@8f10215 and/or https://review.openstack.org/#/c/447785/ for details.