Bug 1661153: Removes _ensure_zstd() and usages r=firefox-build-system-reviewers,glandium

Removes a bunch of zstandard installations that were ran from
within the mach virtualenv, which should already have zstandard
installed.

Differential Revision: https://phabricator.services.mozilla.com/D98387

python/mozbuild/mozbuild/artifact_commands.py

@@ -605,20 +605,7 @@ class PackageFrontend(MachCommandBase):
                     "sha256": h.hexdigest(),
                 }
             if record.unpack and not no_unpack:
-                # Try to unpack the file. If we get an exception importing
-                # zstandard when calling unpack_file, we can try installing
-                # zstandard locally and trying again
-                try:
-                    unpack_file(local)
-                except ImportError as e:
-                    # Need to do this branch while this code is still exercised
-                    # by Python 2.
-                    if six.PY3 and e.name != "zstandard":
-                        raise
-                    elif six.PY2 and e.message != "No module named zstandard":
-                        raise
-                    self._ensure_zstd()
-                    unpack_file(local)
+                unpack_file(local)
                 os.unlink(local)
 
         if not downloaded:

python/mozbuild/mozbuild/artifacts.py

@@ -401,7 +401,6 @@ class ArtifactJob(object):
             for filename in reader.entries:
                 yield filename, reader[filename]
         elif filename.endswith(".tar.zst") and self._mozbuild is not None:
-            self._mozbuild._ensure_zstd()
             import zstandard
 
             ctx = zstandard.ZstdDecompressor()

taskcluster/mach_commands.py

@@ -624,7 +624,6 @@ class TaskClusterImagesProvider(MachCommandBase):
         "or mozilla-inbound)",
     )
     def load_image(self, image_name, task_id, tag):
-        self._ensure_zstd()
         from taskgraph.docker import load_image_by_name, load_image_by_task_id
 
         if not image_name and not task_id: