Add indirection for changes in empy 3 vs 4 (#261)

* Update to use empy 4.0 API
Working towards #259
This is not backwards compatible at the moment. But works with empy==4.0

* Add indirection for changes in empy 3 vs 4
Fixes  #259

* remove now unnecessary imports

src/rocker/em.py

@@ -0,0 +1,23 @@
+# Copyright 2019 Open Source Robotics Foundation
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+import em
+
+def empy_expand(template, substitution_variables):
+    """Indirection for empy version compatibility."""
+    if em.__version__.startswith('3'):
+        return em.expand(template, substitution_variables)
+    else:
+        return em.expand(template, globals=substitution_variables)

src/rocker/extensions.py

@@ -15,7 +15,6 @@
 import grp
 import os
 import docker
-import em
 import getpass
 import pwd
 import pkgutil
@@ -25,6 +24,7 @@
 import sys
 
 from .core import get_docker_client
+from .em import empy_expand
 
 
 def name_to_argument(name):
@@ -81,7 +81,7 @@ def get_preamble(self, cliargs):
 
     def get_snippet(self, cliargs):
         snippet = pkgutil.get_data('rocker', 'templates/%s_snippet.Dockerfile.em' % self.name).decode('utf-8')
-        return em.expand(snippet, self.get_environment_subs())
+        return empy_expand(snippet, self.get_environment_subs())
 
     @staticmethod
     def register_arguments(parser, defaults={}):
@@ -238,7 +238,7 @@ def get_preamble(self, cliargs):
 
     def get_snippet(self, cliargs):
         snippet = pkgutil.get_data('rocker', 'templates/%s_snippet.Dockerfile.em' % self.name).decode('utf-8')
-        return em.expand(snippet, self.get_environment_subs())
+        return empy_expand(snippet, self.get_environment_subs())
 
     def get_docker_args(self, cliargs):
         args = ' -v /run/user/%(user_id)s/pulse:/run/user/%(user_id)s/pulse --device /dev/snd '\
@@ -318,7 +318,7 @@ def get_snippet(self, cliargs):
                 substitutions['shell'] = None
             else:
                 substitutions['shell'] =  cliargs['user_override_shell']
-        return em.expand(snippet, substitutions)
+        return empy_expand(snippet, substitutions)
 
     @staticmethod
     def register_arguments(parser, defaults={}):

src/rocker/nvidia_extension.py

@@ -13,7 +13,6 @@
 # limitations under the License.
 
 import os
-import em
 import getpass
 import tempfile
 from packaging.version import Version
@@ -27,6 +26,8 @@
 from .extensions import name_to_argument
 from .core import get_docker_client
 from .core import RockerExtension
+from .em import empy_expand
+
 
 def get_docker_version():
     docker_version_raw = get_docker_client().version()['Version']
@@ -116,11 +117,11 @@ def get_environment_subs(self, cliargs={}):
 
     def get_preamble(self, cliargs):
         preamble = pkgutil.get_data('rocker', 'templates/%s_preamble.Dockerfile.em' % self.name).decode('utf-8')
-        return em.expand(preamble, self.get_environment_subs(cliargs))
+        return empy_expand(preamble, self.get_environment_subs(cliargs))
 
     def get_snippet(self, cliargs):
         snippet = pkgutil.get_data('rocker', 'templates/%s_snippet.Dockerfile.em' % self.name).decode('utf-8')
-        return em.expand(snippet, self.get_environment_subs(cliargs))
+        return empy_expand(snippet, self.get_environment_subs(cliargs))
 
     def get_docker_args(self, cliargs):
         force_flag = cliargs.get('nvidia', None)
@@ -184,11 +185,11 @@ def get_environment_subs(self, cliargs={}):
     def get_preamble(self, cliargs):
         return ''
         # preamble = pkgutil.get_data('rocker', 'templates/%s_preamble.Dockerfile.em' % self.name).decode('utf-8')
-        # return em.expand(preamble, self.get_environment_subs(cliargs))
+        # return empy_expand(preamble, self.get_environment_subs(cliargs))
 
     def get_snippet(self, cliargs):
         snippet = pkgutil.get_data('rocker', 'templates/%s_snippet.Dockerfile.em' % self.name).decode('utf-8')
-        return em.expand(snippet, self.get_environment_subs(cliargs))
+        return empy_expand(snippet, self.get_environment_subs(cliargs))
 
     def get_docker_args(self, cliargs):
         return ""