--- a/autoland/autoland/autoland.py
+++ b/autoland/autoland/autoland.py
@@ -12,17 +12,17 @@ import time
 import traceback
 
 sys.path.insert(0, os.path.normpath(os.path.join(os.path.normpath(
                 os.path.abspath(os.path.dirname(__file__))), '..',
                                                              '..',
                                                              'pylib',
                                                              'mozautomation')))
 
-import transplant
+from transplant import Transplant
 import treestatus
 
 
 # max attempts to transplant before bailing
 MAX_TRANSPLANT_ATTEMPTS = 50
 
 # max updates to post to reviewboard / iteration
 MOZREVIEW_COMMENT_LIMIT = 10
@@ -115,19 +115,24 @@ def handle_pending_transplants(dbconn):
 
             # TODO: We should break the transplant call into two steps, one
             #       to pull down the commits to transplant, and another
             #       one to rebase it and attempt to push so we don't
             #       duplicate work unnecessarily if we have to rebase more
             #       than once.
             os.environ['AUTOLAND_REQUEST_USER'] = requester
             try:
-                result = transplant.transplant(tree, destination, rev,
-                                               trysyntax, push_bookmark,
-                                               commit_descriptions)
+                with Transplant(tree, destination, rev) as tp:
+                    if trysyntax:
+                        result = tp.push_try(str(trysyntax))
+                    elif push_bookmark:
+                        result = tp.push_bookmark(commit_descriptions,
+                                                  push_bookmark)
+                    else:
+                        result = tp.push(commit_descriptions)
                 landed = True
             except Exception as e:
                 result = str(e)
                 landed = False
             finally:
                 del os.environ['AUTOLAND_REQUEST_USER']
 
             logger.info('transplant from tree: %s rev: %s attempt: %s: %s' % (

--- a/autoland/autoland/transplant.py
+++ b/autoland/autoland/transplant.py
@@ -16,94 +16,84 @@ class HgCommandError(Exception):
         # we want to strip out any sensitive --config options
         hg_args = map(lambda x: x if not x.startswith('bugzilla') else 'xxx',
                       hg_args)
         message = 'hg error in cmd: hg %s: %s' % (' '.join(hg_args),
                                                   out.getvalue())
         super(self.__class__, self).__init__(message)
 
 
-def transplant(tree, destination, rev, trysyntax=None,
-               push_bookmark=False, commit_descriptions=None):
-    """Transplant a specified revision and ancestors to the specified tree.
-
-    If ``trysyntax`` is specified, a Try commit will be created using the
-    syntax specified.
-    """
-    # These values can appear in command arguments. Don't let unicode leak
-    # into these.
-    assert isinstance(tree, str)
-    assert isinstance(destination, str)
-    assert isinstance(rev, str)
-    if push_bookmark:
-        assert isinstance(push_bookmark, str)
+class Transplant(object):
+    """Transplant a specified revision and ancestors to the specified tree."""
 
-    path = config.get('repos').get(tree,
-                                   os.path.join(os.path.sep, 'repos', tree))
-    configs = ['ui.interactive=False']
-    with hglib.open(path, encoding='utf-8', configs=configs) as hg_repo:
-        tp = Transplant(hg_repo, tree, destination, rev)
-
-        if trysyntax:
-            return tp.push_try(trysyntax)
+    def __init__(self, tree, destination, rev):
+        # These values can appear in command arguments. Don't let unicode leak
+        # into these.
+        assert isinstance(tree, str), "tree arg is not str"
+        assert isinstance(destination, str), "destination arg is not str"
+        assert isinstance(rev, str), "rev arg is not str"
 
-        elif push_bookmark:
-            return tp.push_bookmark(commit_descriptions, push_bookmark)
-
-        else:
-            return tp.push(commit_descriptions)
-
-
-class Transplant:
-    def __init__(self, hg_repo, tree, destination, rev):
-        self.hg_repo = hg_repo
         self.tree = tree
         self.destination = destination
         self.source_rev = rev
 
+    def __enter__(self):
+        path = config.get('repos').get(
+            self.tree, os.path.join(os.path.sep, 'repos', self.tree))
+        configs = ['ui.interactive=False']
+        self.hg_repo = hglib.open(path, encoding='utf-8', configs=configs)
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.strip_drafts()
+        self.hg_repo.close()
+
     def push_try(self, trysyntax):
+        # Don't let unicode leak into command arguments.
+        assert isinstance(trysyntax, str), "trysyntax arg is not str"
+
         self.update_repo()
 
         if not trysyntax.startswith("try: "):
             trysyntax = "try: %s" % trysyntax
         rev = self.run_hg_cmds([
             [
                 '--encoding=utf-8',
                 '--config', 'ui.allowemptycommit=true',
                 'commit',
                 '-m', trysyntax
             ],
             ['push', '-r', '.', '-f', 'try'],
             ['log', '-r', 'tip', '-T', '{node|short}'],
         ])
 
-        self.strip_drafts()
         return rev
 
     def push_bookmark(self, commit_descriptions, bookmark):
+        # Don't let unicode leak into command arguments.
+        assert isinstance(bookmark, str), "bookmark arg is not str"
+
         remote_tip = self.update_repo()
 
         rev = self.apply_changes(remote_tip, commit_descriptions)
         self.run_hg_cmds([
             ['bookmark', bookmark],
             ['push', '-B', bookmark, self.destination],
         ])
 
-        self.strip_drafts()
         return rev
 
     def push(self, commit_descriptions):
         remote_tip = self.update_repo()
 
         rev = self.apply_changes(remote_tip, commit_descriptions)
         self.run_hg_cmds([
             ['push', '-r', 'tip', self.destination]
         ])
 
-        self.strip_drafts()
         return rev
 
     def update_repo(self):
         # Obtain remote tip. We assume there is only a single head.
         remote_tip = self.get_remote_tip()
 
         # Strip any lingering draft changesets.
         self.strip_drafts()