britney: Skip architectures not listed in Release files

As a side effect, remove mips64el from NEW_ARCHES as we no longer need
that as a work around.

Closes: Debian/britney2#12
Signed-off-by: Niels Thykier <niels@thykier.net>

britney.conf

@@ -37,7 +37,7 @@ OUTOFSYNC_ARCHES  =
 BREAK_ARCHES      =
 
 # if you're in this list, you are a new architecture
-NEW_ARCHES        = mips64el
+NEW_ARCHES        =
 
 # priorities and delays
 MINDAYS_LOW       = 10

britney.py

@@ -207,7 +207,7 @@ from britney2.utils import (old_libraries_format, undo_changes,
                             write_excuses, write_heidi_delta, write_controlfiles,
                             old_libraries, is_nuninst_asgood_generous,
                             clone_nuninst, check_installability,
-                            create_provides_map,
+                            create_provides_map, read_release_file,
                             )
 
 __author__ = 'Fabio Tranchitella and the Debian Release Team'
@@ -999,21 +999,21 @@ class Britney(object):
         arch2packages = {}
 
         if self.options.components:
+            release_file = read_release_file(basedir)
+            listed_archs = set(release_file['Architectures'].split())
             for arch in architectures:
                 packages = {}
+                if arch not in listed_archs:
+                    self.log("Skipping arch %s for %s: It is not listed in the Release file" % (arch, distribution))
+                    arch2packages[arch] = ({}, {})
+                    continue
                 for component in self.options.components:
                     binary_dir = "binary-%s" % arch
                     filename = os.path.join(basedir,
                                             component,
                                             binary_dir,
                                             'Packages')
-                    try:
                     filename = possibly_compressed(filename)
-                    except FileNotFoundError:
-                        if arch not in self.options.new_arches:
-                            raise
-                        self.log("Ignoring missing file for new arch %s: %s" % (arch, filename))
-                        continue
                     udeb_filename = os.path.join(basedir,
                                                  component,
                                                  "debian-installer",

britney2/utils.py

@@ -21,6 +21,7 @@
 # GNU General Public License for more details.
 
 
+import apt_pkg
 import errno
 import os
 import time
@@ -670,3 +671,18 @@ def create_provides_map(packages):
             provides[provided_pkg].add((pkg, provided_version))
 
     return provides
+
+
+def read_release_file(suite_dir):
+    """Parses a given "Release" file
+
+    :param suite_dir: The directory to the suite
+    :return: A dict of the first (and only) paragraph in an Release file
+    """
+    release_file = os.path.join(suite_dir, 'Release')
+    with open(release_file) as fd:
+        tag_file = iter(apt_pkg.TagFile(fd))
+        result = next(tag_file)
+        if next(tag_file, None) is not None:
+            raise TypeError("%s has more than one paragraph" % release_file)
+    return result

britney_nobreakall.conf

@@ -37,7 +37,7 @@ OUTOFSYNC_ARCHES  =
 BREAK_ARCHES      =
 
 # if you're in this list, you are a new architecture
-NEW_ARCHES        = mips64el
+NEW_ARCHES        =
 
 # priorities and delays
 MINDAYS_LOW       = 10