mbox locking: omit dotlock if we don't have the permissions to create it

Closes: issue #855269.

archivemail.py

@@ -407,8 +407,16 @@ class Mbox(mailbox.UnixMailbox):
         pid = os.getpid()
         box_dir, prelock_prefix = os.path.split(self.mbox_file_name)
         prelock_suffix = ".%s.%s%s" % (hostname, pid, options.lockfile_extension)
-        plfd, prelock_name = tempfile.mkstemp(prelock_suffix, prelock_prefix,
-            dir=box_dir)
+        try:
+            plfd, prelock_name = tempfile.mkstemp(prelock_suffix, prelock_prefix,
+                dir=box_dir)
+        except OSError, e:
+            if e.errno == errno.EACCES:
+                if not options.quiet:
+                    user_warning("no write permissions: omitting dotlock for '%s'" % \
+                        self.mbox_file_name)
+                return
+            raise
         lock_name = self.mbox_file_name + options.lockfile_extension
         try:
             try:

test_archivemail.py

@@ -120,6 +120,17 @@ class TestMboxDotlock(TestCaseInTempdir):
         self.mbox._dotlock_unlock()
         assert(not os.path.isfile(lock))
 
+    def testDotlockingSucceedsUponEACCES(self):
+        """A dotlock should silently be omitted upon EACCES."""
+        archivemail.options.quiet = True
+        mbox_dir = os.path.dirname(self.mbox_name)
+        os.chmod(mbox_dir, 0500)
+        try:
+            self.mbox._dotlock_lock()
+        finally:
+            os.chmod(mbox_dir, 0700)
+            archivemail.options.quiet = False
+
 class TestMboxPosixLock(TestCaseInTempdir):
     def setUp(self):
         super(TestMboxPosixLock, self).setUp()