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diff --git a/contrail-controller/hooks/charmhelpers/core/templating.py b/contrail-controller/hooks/charmhelpers/core/templating.py
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+# Copyright 2014-2015 Canonical Limited.
+#
+# 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 os
+import sys
+
+from charmhelpers.core import host
+from charmhelpers.core import hookenv
+
+
+def render(source, target, context, owner='root', group='root',
+ perms=0o444, templates_dir=None, encoding='UTF-8', template_loader=None):
+ """
+ Render a template.
+
+ The `source` path, if not absolute, is relative to the `templates_dir`.
+
+ The `target` path should be absolute. It can also be `None`, in which
+ case no file will be written.
+
+ The context should be a dict containing the values to be replaced in the
+ template.
+
+ The `owner`, `group`, and `perms` options will be passed to `write_file`.
+
+ If omitted, `templates_dir` defaults to the `templates` folder in the charm.
+
+ The rendered template will be written to the file as well as being returned
+ as a string.
+
+ Note: Using this requires python-jinja2 or python3-jinja2; if it is not
+ installed, calling this will attempt to use charmhelpers.fetch.apt_install
+ to install it.
+ """
+ try:
+ from jinja2 import FileSystemLoader, Environment, exceptions
+ except ImportError:
+ try:
+ from charmhelpers.fetch import apt_install
+ except ImportError:
+ hookenv.log('Could not import jinja2, and could not import '
+ 'charmhelpers.fetch to install it',
+ level=hookenv.ERROR)
+ raise
+ if sys.version_info.major == 2:
+ apt_install('python-jinja2', fatal=True)
+ else:
+ apt_install('python3-jinja2', fatal=True)
+ from jinja2 import FileSystemLoader, Environment, exceptions
+
+ if template_loader:
+ template_env = Environment(loader=template_loader)
+ else:
+ if templates_dir is None:
+ templates_dir = os.path.join(hookenv.charm_dir(), 'templates')
+ template_env = Environment(loader=FileSystemLoader(templates_dir))
+ try:
+ source = source
+ template = template_env.get_template(source)
+ except exceptions.TemplateNotFound as e:
+ hookenv.log('Could not load template %s from %s.' %
+ (source, templates_dir),
+ level=hookenv.ERROR)
+ raise e
+ content = template.render(context)
+ if target is not None:
+ target_dir = os.path.dirname(target)
+ if not os.path.exists(target_dir):
+ # This is a terrible default directory permission, as the file
+ # or its siblings will often contain secrets.
+ host.mkdir(os.path.dirname(target), owner, group, perms=0o755)
+ host.write_file(target, content.encode(encoding), owner, group, perms)
+ return content