diff --git a/mach b/mach
index 1a4869ada6605..a849560367eba 100755
--- a/mach
+++ b/mach
@@ -14,7 +14,6 @@ py2commands="
     analyze
     android
     android-emulator
-    artifact
     awsy-test
     browsertime
     cargo
diff --git a/python/mozbuild/mozbuild/action/tooltool.py b/python/mozbuild/mozbuild/action/tooltool.py
index 9d966f7420a9b..cfd692da0cbd8 100755
--- a/python/mozbuild/mozbuild/action/tooltool.py
+++ b/python/mozbuild/mozbuild/action/tooltool.py
@@ -705,7 +705,7 @@ def open_manifest(manifest_file):
     """I know how to take a filename and load it into a Manifest object"""
     if os.path.exists(manifest_file):
         manifest = Manifest()
-        with open(manifest_file, "rb") as f:
+        with open(manifest_file, "r" if PY3 else "rb") as f:
             manifest.load(f)
             log.debug("loaded manifest from file '%s'" % manifest_file)
         return manifest
diff --git a/python/mozbuild/mozbuild/artifact_cache.py b/python/mozbuild/mozbuild/artifact_cache.py
index 14775c28c0309..7230e86542750 100644
--- a/python/mozbuild/mozbuild/artifact_cache.py
+++ b/python/mozbuild/mozbuild/artifact_cache.py
@@ -162,7 +162,7 @@ def fetch(self, url, force=False):
             if len(fname) not in (32, 40, 56, 64, 96, 128):
                 raise TypeError()
             binascii.unhexlify(fname)
-        except TypeError:
+        except (TypeError, binascii.Error):
             # We download to a temporary name like HASH[:16]-basename to
             # differentiate among URLs with the same basenames.  We used to then
             # extract the build ID from the downloaded artifact and use it to make a
diff --git a/python/mozbuild/mozbuild/artifact_commands.py b/python/mozbuild/mozbuild/artifact_commands.py
index a161c90edbc8e..3488a3429af1d 100644
--- a/python/mozbuild/mozbuild/artifact_commands.py
+++ b/python/mozbuild/mozbuild/artifact_commands.py
@@ -412,7 +412,7 @@ def __init__(self, task_id, artifact_name):
             # Keep a sha256 of each downloaded file, for the chain-of-trust
             # validation.
             if artifact_manifest is not None:
-                with open(local) as fh:
+                with open(local, 'rb') as fh:
                     h = hashlib.sha256()
                     while True:
                         data = fh.read(1024 * 1024)
diff --git a/python/mozbuild/mozbuild/artifacts.py b/python/mozbuild/mozbuild/artifacts.py
index c9cf28640fc2f..edb68010617f4 100644
--- a/python/mozbuild/mozbuild/artifacts.py
+++ b/python/mozbuild/mozbuild/artifacts.py
@@ -897,6 +897,7 @@ def run_hg(self, *args, **kwargs):
         env = kwargs.get('env', {})
         env['HGPLAIN'] = '1'
         kwargs['env'] = ensure_subprocess_env(env)
+        kwargs['universal_newlines'] = True
         return subprocess.check_output([self._hg] + list(args),
                                        **kwargs)
 
@@ -979,11 +980,11 @@ def _get_hg_revisions_from_git(self):
             self._git, 'rev-list', '--topo-order',
             '--max-count={num}'.format(num=NUM_REVISIONS_TO_QUERY),
             'HEAD',
-        ], cwd=self._topsrcdir)
+        ], universal_newlines=True, cwd=self._topsrcdir)
 
         hg_hash_list = subprocess.check_output([
             self._git, 'cinnabar', 'git2hg'
-        ] + rev_list.splitlines(), cwd=self._topsrcdir)
+        ] + rev_list.splitlines(), universal_newlines=True, cwd=self._topsrcdir)
 
         zeroes = "0" * 40
 
@@ -1201,7 +1202,8 @@ def install_from_revset(self, revset, distdir):
             elif self._git:
                 revset = subprocess.check_output([
                     self._git, 'rev-parse', '%s^{commit}' % revset],
-                    stderr=open(os.devnull, 'w'), cwd=self._topsrcdir).strip()
+                    stderr=open(os.devnull, 'w'), universal_newlines=True,
+                    cwd=self._topsrcdir).strip()
             else:
                 # Fallback to the exception handling case from both hg and git
                 raise subprocess.CalledProcessError()
@@ -1215,7 +1217,8 @@ def install_from_revset(self, revset, distdir):
 
         if revision is None and self._git:
             revision = subprocess.check_output(
-                [self._git, 'cinnabar', 'git2hg', revset], cwd=self._topsrcdir).strip()
+                [self._git, 'cinnabar', 'git2hg', revset], universal_newlines=True,
+                cwd=self._topsrcdir).strip()
 
         if revision == "0" * 40 or revision is None:
             raise ValueError('revision specification must resolve to a commit known to hg')