Implement utility enumeration for policyrep classes.

Requires enum34 (not enum) package for Python < 3.4.

README.md

@@ -17,6 +17,7 @@ To run SETools command line tools, the following packages are required:
 * Python 2.7 or 3.3+
 * NetworkX 1.8+
 * setuptools
+* enum34 (on Python 2.7 and 3.3 only)
 * libselinux Python bindings (optional but recommended)
 
 To run SETools graphical tools, the following packages are also required:

setools/policyrep/util.py

@@ -0,0 +1,62 @@
+# Copyright 2016, Chris PeBenito <pebenito@ieee.org>
+#
+# This file is part of SETools.
+#
+# SETools is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as
+# published by the Free Software Foundation, either version 2.1 of
+# the License, or (at your option) any later version.
+#
+# SETools is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with SETools.  If not, see
+# <http://www.gnu.org/licenses/>.
+#
+import warnings
+
+from enum import Enum
+
+
+class PolicyEnum(Enum):
+
+    """
+    Base class for policy enumerations.
+
+    Standard Enum behavior except for returning
+    the enum name for the default string representation
+    and basic string format.
+    """
+
+    def __str__(self):
+        return self.name
+
+    def __format__(self, spec):
+        if not spec:
+            return self.name
+        else:
+            return super(PolicyEnum, self).__format__(spec)
+
+    def __eq__(self, other):
+        if isinstance(other, str):
+            warnings.warn("{} has changed to an enumeration.  In the future, direct string "
+                          "comparisons will be deprecated.".format(self.__class__.__name__),
+                          PendingDeprecationWarning)
+            return self.name == other
+        else:
+            return super(PolicyEnum, self).__eq__(other)
+
+    def __hash__(self):
+        return hash(self.name)
+
+    @classmethod
+    def lookup(cls, value):
+        """Look up an enumeration by name or value."""
+
+        try:
+            return cls(value)
+        except ValueError:
+            return cls[value]

tox.ini

@@ -21,6 +21,7 @@ commands        = pep8 --version
 basepython      = python3.3
 deps            = networkx==1.9
                   coverage
+                  enum34
 commands        = coverage --version
                   coverage erase
                   coverage run setup.py test
@@ -31,6 +32,7 @@ basepython      = python3.3
 deps            = pylint
                   networkx==1.9
                   mock
+                  enum34
 commands        = {envpython} setup.py build_ext -i
                   pylint --version
                   pylint -E --rcfile .pylintrc setools tests seinfo seinfoflow sedta sesearch sediff
@@ -40,5 +42,7 @@ commands        = {envpython} setup.py build_ext -i
 [testenv]
 deps            = networkx==1.9
                   py27: mock
+                  py27: enum34
+                  py33: enum34
 commands        = {envpython} setup.py test
 recreate        = True