britney -> util: Extract a "create_provides_map"

Signed-off-by: Niels Thykier <niels@thykier.net>

britney.py

@@ -205,7 +205,9 @@ from britney_util import (old_libraries_format, undo_changes,
                           eval_uninst, newly_uninst, make_migrationitem,
                           write_excuses, write_heidi_delta, write_controlfiles,
                           old_libraries, is_nuninst_asgood_generous,
-                          clone_nuninst, check_installability)
+                          clone_nuninst, check_installability,
+                          create_provides_map,
+                          )
 from policies.policy import AgePolicy, RCBugPolicy, PolicyVerdict
 from consts import (VERSION, SECTION, BINARIES, MAINTAINER, FAKESRC,
                    SOURCE, SOURCEVER, ARCHITECTURE, CONFLICTS, DEPENDS,
@@ -1014,13 +1016,7 @@ class Britney(object):
                              self.sources[distribution])
 
         # create provides
-        provides = defaultdict(set)
+        provides = create_provides_map(packages)
-
-        for pkg, dpkg in packages.items():
-            # register virtual packages and real packages that provide
-            # them
-            for provided_pkg, provided_version, _ in dpkg[PROVIDES]:
-                provides[provided_pkg].add((pkg, provided_version))
 
         # return a tuple with the list of real and virtual packages
         return (packages, provides)

britney_util.py

@@ -21,6 +21,7 @@
 # GNU General Public License for more details.
 
 
+from collections import defaultdict
 from functools import partial
 from datetime import datetime
 from itertools import filterfalse
@@ -654,3 +655,21 @@ def possibly_compressed(path, permitted_compressesion=None):
         if os.path.exists(cpath):
             return cpath
     raise FileNotFoundError(errno.ENOENT, os.strerror(errno.ENOENT), path)
+
+
+def create_provides_map(packages):
+    """Create a provides map from a map binary package names and thier BinaryPackage objects
+
+    :param packages: A dict mapping binary package names to their BinaryPackage object
+    :return: A provides map
+    """
+    # create provides
+    provides = defaultdict(set)
+
+    for pkg, dpkg in packages.items():
+        # register virtual packages and real packages that provide
+        # them
+        for provided_pkg, provided_version, _ in dpkg[PROVIDES]:
+            provides[provided_pkg].add((pkg, provided_version))
+
+    return provides