Refactor to avoid empty "pu" and "tpu" data structures

Previously, we would always create empty data structures for "pu" and
"tpu" if these optional suites were not configured.  However, we only
reference "pu" and "tpu" directly in very few spots that can easily be
rewritten.

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

britney.py

@@ -317,19 +317,14 @@ class Britney(object):
                 return
 
         self.all_binaries = {}
-        # read the source and binary packages for the involved distributions
-        self.sources['testing'] = self.read_sources(self.suite_info['testing'].path)
-        self.sources['unstable'] = self.read_sources(self.suite_info['unstable'].path)
-        for suite in ('tpu', 'pu'):
-            if hasattr(self.options, suite):
-                self.sources[suite] = self.read_sources(getattr(self.options, suite))
-            else:
-                self.sources[suite] = {}
-
-        self.binaries['testing'] = {}
-        self.binaries['unstable'] = {}
-        self.binaries['tpu'] = {}
-        self.binaries['pu'] = {}
+        # read the source and binary packages for the involved distributions.  Notes:
+        # - Load testing last as some live-data tests have more complete information in
+        #   unstable
+        # - Load all sources before any of the binaries.
+        for suite in self.suite_info:
+            sources = self.read_sources(suite.path)
+            self.sources[suite.name] = sources
+            self.binaries[suite.name] = self.read_binaries(suite.path, suite.name, self.options.architectures)
 
         # compute inverse Testsuite-Triggers: map, unifying all series
         self.logger.info('Building inverse testsuite_triggers map')
@@ -339,20 +334,6 @@ class Britney(object):
                 for trigger in data.testsuite_triggers:
                     self.testsuite_triggers.setdefault(trigger, set()).add(src)
 
-        self.binaries['unstable'] = self.read_binaries(self.suite_info['unstable'].path, "unstable", self.options.architectures)
-        for suite in ('tpu', 'pu'):
-            if suite in self.suite_info:
-                self.binaries[suite] = self.read_binaries(self.suite_info[suite].path, suite, self.options.architectures)
-            else:
-                # _build_installability_tester relies on this being
-                # properly initialised, so insert two empty dicts
-                # here.
-                for arch in self.options.architectures:
-                    self.binaries[suite][arch] = ({}, {})
-        # Load testing last as some live-data tests have more complete information in
-        # unstable
-        self.binaries['testing'] = self.read_binaries(self.suite_info['testing'].path, "testing", self.options.architectures)
-
         try:
             constraints_file = os.path.join(self.options.static_input_dir, 'constraints')
             faux_packages = os.path.join(self.options.static_input_dir, 'faux-packages')
@@ -514,6 +495,7 @@ class Britney(object):
                 if suite in {'testing', 'unstable'}:  # pragma: no cover
                     self.logger.error("Mandatory configuration %s is not set in the config", suite.upper())
                     sys.exit(1)
+                # self.suite_info[suite] = SuiteInfo(name=suite, path=None, excuses_suffix=suffix)
                 self.logger.info("Optional suite %s is not defined (config option: %s) ", suite, suite.upper())
 
         self.suite_info = Suites(suites[0], suites[1:])
@@ -1632,19 +1614,19 @@ class Britney(object):
             if should_upgrade_src(pkg, 'unstable'):
                 upgrade_me_add(pkg)
 
-        # for every source package in *-proposed-updates, check if it should be upgraded
-        for suite in ['pu', 'tpu']:
-            for pkg in sources[suite]:
+        # for every source package in the additional source suites, check if it should be upgraded
+        for suite in self.suite_info.additional_source_suites:
+            for pkg in sources[suite.name]:
                 # if the source package is already present in testing,
                 # check if it should be upgraded for every binary package
                 if pkg in testing:
                     for arch in architectures:
-                        if should_upgrade_srcarch(pkg, arch, suite):
-                            upgrade_me_add("%s/%s_%s" % (pkg, arch, suite))
+                        if should_upgrade_srcarch(pkg, arch, suite.name):
+                            upgrade_me_add("%s/%s_%s" % (pkg, arch, suite.name))
 
                 # check if the source package should be upgraded
-                if should_upgrade_src(pkg, suite):
-                    upgrade_me_add("%s_%s" % (pkg, suite))
+                if should_upgrade_src(pkg, suite.name):
+                    upgrade_me_add("%s_%s" % (pkg, suite.name))
 
         # process the `remove' hints, if the given package is not yet in upgrade_me
         for hint in self.hints['remove']:
@@ -2686,6 +2668,8 @@ class Britney(object):
             rightversion = inunstable and (apt_pkg.version_compare(self.sources['unstable'][pkg.package].version, pkg.version) == 0)
             if pkg.suite == 'unstable' and not rightversion:
                 for suite in ['pu', 'tpu']:
+                    if suite not in self.suite_info:
+                        continue
                     if pkg.package in self.sources[suite] and apt_pkg.version_compare(self.sources[suite][pkg.package].version, pkg.version) == 0:
                         pkg.suite = suite
                         _pkgvers[idx] = pkg
@@ -2693,7 +2677,7 @@ class Britney(object):
 
             # handle *-proposed-updates
             if pkg.suite in ['pu', 'tpu']:
-                if pkg.package not in self.sources[pkg.suite]:
+                if pkg.suite not in self.suite_info or pkg.package not in self.sources[pkg.suite]:
                     continue
                 if apt_pkg.version_compare(self.sources[pkg.suite][pkg.package].version, pkg.version) != 0:
                     issues.append("Version mismatch, %s %s != %s" % (pkg.package, pkg.version,