autopkgtest.py: Document method read() and code simplification

britney.py: code simplification

autopkgtest.py

@@ -96,6 +96,18 @@ class AutoPackageTest(object):
                     yield linebits
 
     def read(self):
+        '''Loads a list of results
+
+        This function loads a list of results returned by __parse() and builds
+        2 lists:
+            - a list of source package/version with all the causes that
+            triggered a test and the result of the test for this trigger.
+            - a list of packages/version that triggered a test with the source
+            package/version and result triggered by this package.
+        These lists will be used in result() called from britney.py to generate
+        excuses and now which uploads passed, caused regression or which tests
+        have always been failing
+        '''
         self.pkglist = defaultdict(dict)
         self.pkgcauses = defaultdict(lambda: defaultdict(list))
         for linebits in self._parse(self._result_path):
@@ -109,10 +121,8 @@ class AutoPackageTest(object):
 
             i = iter(linebits[3:])
             for trigsrc, trigver in zip(i, i):
-                if not trigsrc in self.pkglist[src][ver]['causes']:
-                    self.pkglist[src][ver]['causes'][trigsrc] = []
-                self.pkglist[src][ver]['causes'][trigsrc].append((trigver,
-                                                                  status))
+                self.pkglist[src][ver]['causes'].setdefault(
+                    trigsrc, []).append((trigver, status))
                 self.pkgcauses[trigsrc][trigver].append((status, src, ver))
 
     def _adt_britney(self, *args):

britney.py

@@ -1762,9 +1762,7 @@ class Britney(object):
                     private_url = "%s/%s-adt-%s/lastBuild" % (
                         jenkins_private, self.options.adt_series,
                         adtsrc.replace("+", "-"))
-                    adt_label = status
-                    if status in ADT_EXCUSES_LABELS:
-                        adt_label = ADT_EXCUSES_LABELS[status]
+                    adt_label = ADT_EXCUSES_LABELS.get(status, status)
                     e.addhtml(
                         "autopkgtest for %s %s: %s (Jenkins: "
                         "<a href=\"%s\">public</a>, "