diff --git a/cipd.py b/cipd.py
index b906337..fe0eece 100755
--- a/cipd.py
+++ b/cipd.py
@@ -20,182 +20,190 @@
 
 
 SCRIPT_DIR = os.path.dirname(__file__)
-VERSION_FILE = os.path.join(SCRIPT_DIR, '.cipd_version')
-DIGESTS_FILE = VERSION_FILE + '.digests'
+VERSION_FILE = os.path.join(SCRIPT_DIR, ".cipd_version")
+DIGESTS_FILE = VERSION_FILE + ".digests"
 # Put CIPD client in tools so that users can easily get it in their PATH.
-CLIENT = os.path.join(SCRIPT_DIR, 'tools', 'cipd')
-CIPD_HOST = 'chrome-infra-packages.appspot.com'
+CLIENT = os.path.join(SCRIPT_DIR, "tools", "cipd")
+CIPD_HOST = "chrome-infra-packages.appspot.com"
 
 
 def platform_normalized():
-  """Normalize platform into format expected in CIPD paths."""
+    """Normalize platform into format expected in CIPD paths."""
 
-  try:
-    os_name = platform.system().lower()
-    return {
-        'linux': 'linux',
-        'mac': 'mac',
-        'darwin': 'mac',
-        'windows': 'windows',
-    }[os_name]
-  except KeyError:
-    raise Exception('unrecognized os: {}'.format(os_name))
+    try:
+        os_name = platform.system().lower()
+        return {"linux": "linux", "mac": "mac", "darwin": "mac", "windows": "windows",}[
+            os_name
+        ]
+    except KeyError:
+        raise Exception("unrecognized os: {}".format(os_name))
 
 
 def arch_normalized():
-  """Normalize arch into format expected in CIPD paths."""
+    """Normalize arch into format expected in CIPD paths."""
 
-  machine = platform.machine()
-  if machine.startswith('arm'):
-    return machine
-  if machine.endswith('64'):
-    return 'amd64'
-  if machine.endswith('86'):
-    return '386'
-  raise Exception('unrecognized arch: {}'.format(machine))
+    machine = platform.machine()
+    if machine.startswith("arm"):
+        return machine
+    if machine.endswith("64"):
+        return "amd64"
+    if machine.endswith("86"):
+        return "386"
+    raise Exception("unrecognized arch: {}".format(machine))
 
 
 def user_agent():
-  try:
-    rev = subprocess.check_output(
-        ['git', '-C', SCRIPT_DIR, 'rev-parse', 'HEAD']).strip()
-  except subprocess.CalledProcessError:
-    rev = '???'
-  return 'fuchsia-infra/tools/{}'.format(rev)
+    try:
+        rev = subprocess.check_output(
+            ["git", "-C", SCRIPT_DIR, "rev-parse", "HEAD"]
+        ).strip()
+    except subprocess.CalledProcessError:
+        rev = "???"
+    return "fuchsia-infra/tools/{}".format(rev)
 
 
 def actual_hash(path):
-  hasher = hashlib.sha256()
-  with open(path, 'rb') as ins:
-    hasher.update(ins.read())
-  return hasher.hexdigest()
+    hasher = hashlib.sha256()
+    with open(path, "rb") as ins:
+        hasher.update(ins.read())
+    return hasher.hexdigest()
 
 
 def expected_hash():
-  """Pulls expected hash from digests file."""
+    """Pulls expected hash from digests file."""
 
-  with open(DIGESTS_FILE, 'r') as ins:
-    for line in ins:
-      line = line.strip()
-      if line.startswith('#') or not line:
-        continue
-      plat, hashtype, hashval = line.split()
-      if (hashtype == 'sha256' and
-          plat == '{}-{}'.format(platform_normalized(), arch_normalized())):
-        return hashval
-    raise Exception(
-        'platform {} not in {}'.format(platform_normalized(), DIGESTS_FILE))
+    with open(DIGESTS_FILE, "r") as ins:
+        for line in ins:
+            line = line.strip()
+            if line.startswith("#") or not line:
+                continue
+            plat, hashtype, hashval = line.split()
+            if hashtype == "sha256" and plat == "{}-{}".format(
+                platform_normalized(), arch_normalized()
+            ):
+                return hashval
+        raise Exception(
+            "platform {} not in {}".format(platform_normalized(), DIGESTS_FILE)
+        )
 
 
 def client_bytes():
-  """Pull down the CIPD client and return it as a bytes object.
+    """Pull down the CIPD client and return it as a bytes object.
 
   Often CIPD_HOST returns a 302 FOUND with a pointer to storage.googleapis.com,
   so this needs to handle redirects, but it shouldn't require the initial
   response to be a redirect either.
   """
 
-  with open(VERSION_FILE, 'r') as ins:
-    version = ins.read().strip()
+    with open(VERSION_FILE, "r") as ins:
+        version = ins.read().strip()
 
-  conn = httplib.HTTPSConnection(CIPD_HOST)
-  path = '/client?platform={platform}-{arch}&version={version}'.format(
-      platform=platform_normalized(),
-      arch=arch_normalized(),
-      version=version)
+    conn = httplib.HTTPSConnection(CIPD_HOST)
+    path = "/client?platform={platform}-{arch}&version={version}".format(
+        platform=platform_normalized(), arch=arch_normalized(), version=version
+    )
 
-  for _ in range(10):
-    conn.request('GET', path)
-    res = conn.getresponse()
-    # Have to read the response before making a new request, so make sure
-    # we always read it.
-    content = res.read()
+    for _ in range(10):
+        conn.request("GET", path)
+        res = conn.getresponse()
+        # Have to read the response before making a new request, so make sure
+        # we always read it.
+        content = res.read()
 
-    # Found client bytes.
-    if res.status == httplib.OK:
-      return content
+        # Found client bytes.
+        if res.status == httplib.OK:
+            return content
 
-    # Redirecting to another location.
-    elif res.status == httplib.FOUND:
-      location = res.getheader('location')
-      url = urlparse.urlparse(location)
-      if url.netloc != conn.host:
-        conn = httplib.HTTPSConnection(url.netloc)
-      path = '{}?{}'.format(url.path, url.query)
+        # Redirecting to another location.
+        elif res.status == httplib.FOUND:
+            location = res.getheader("location")
+            url = urlparse.urlparse(location)
+            if url.netloc != conn.host:
+                conn = httplib.HTTPSConnection(url.netloc)
+            path = "{}?{}".format(url.path, url.query)
 
-    # Some kind of error in this response.
-    else:
-      break
+        # Some kind of error in this response.
+        else:
+            break
 
-  raise Exception('failed to download client')
+    raise Exception("failed to download client")
 
 
 def bootstrap():
-  """Bootstrap cipd client installation."""
+    """Bootstrap cipd client installation."""
 
-  client_dir = os.path.dirname(CLIENT)
-  if not os.path.isdir(client_dir):
-    os.makedirs(client_dir)
+    client_dir = os.path.dirname(CLIENT)
+    if not os.path.isdir(client_dir):
+        os.makedirs(client_dir)
 
-  print(
-      'Bootstrapping cipd client for {}-{}'.format(
-          platform_normalized(), arch_normalized()))
-  tmp_path = os.path.join(SCRIPT_DIR, 'tools', '.cipd')
-  with open(tmp_path, 'wb') as tmp:
-    tmp.write(client_bytes())
+    print(
+        "Bootstrapping cipd client for {}-{}".format(
+            platform_normalized(), arch_normalized()
+        )
+    )
+    tmp_path = os.path.join(SCRIPT_DIR, "tools", ".cipd")
+    with open(tmp_path, "wb") as tmp:
+        tmp.write(client_bytes())
 
-  expected = expected_hash()
-  actual = actual_hash(tmp_path)
+    expected = expected_hash()
+    actual = actual_hash(tmp_path)
 
-  if expected != actual:
-    raise Exception('digest of downloaded CIPD client is incorrect, check that '
-                    'digests file is current')
+    if expected != actual:
+        raise Exception(
+            "digest of downloaded CIPD client is incorrect, check that "
+            "digests file is current"
+        )
 
-  os.chmod(tmp_path, 0755)
-  os.rename(tmp_path, CLIENT)
+    os.chmod(tmp_path, 0755)
+    os.rename(tmp_path, CLIENT)
 
 
 def selfupdate():
-  """Update cipd client."""
+    """Update cipd client."""
 
-  cmd = [
-      CLIENT,
-      'selfupdate',
-      '-version-file', VERSION_FILE,
-      '-service-url', 'https://{}'.format(CIPD_HOST),
-  ]
-  subprocess.check_call(cmd)
+    cmd = [
+        CLIENT,
+        "selfupdate",
+        "-version-file",
+        VERSION_FILE,
+        "-service-url",
+        "https://{}".format(CIPD_HOST),
+    ]
+    subprocess.check_call(cmd)
 
 
 def init():
-  """Install/update cipd client."""
+    """Install/update cipd client."""
 
-  os.environ['CIPD_HTTP_USER_AGENT_PREFIX'] = user_agent()
-
-  try:
-    if not os.path.isfile(CLIENT):
-      bootstrap()
+    os.environ["CIPD_HTTP_USER_AGENT_PREFIX"] = user_agent()
 
     try:
-      selfupdate()
-    except subprocess.CalledProcessError:
-      print('CIPD selfupdate failed. Bootstrapping then retrying...',
-            file=sys.stderr)
-      bootstrap()
-      selfupdate()
+        if not os.path.isfile(CLIENT):
+            bootstrap()
 
-  except Exception:
-    print('Failed to initialize CIPD. Run '
-          '`CIPD_HTTP_USER_AGENT_PREFIX={user_agent}/manual {client} '
-          "selfupdate -version-file '{version_file}'` "
-          'to diagnose if this is persistent.'.format(
-              user_agent=user_agent(),
-              client=CLIENT,
-              version_file=VERSION_FILE,
-          ), file=sys.stderr)
-    raise
+        try:
+            selfupdate()
+        except subprocess.CalledProcessError:
+            print(
+                "CIPD selfupdate failed. Bootstrapping then retrying...",
+                file=sys.stderr,
+            )
+            bootstrap()
+            selfupdate()
+
+    except Exception:
+        print(
+            "Failed to initialize CIPD. Run "
+            "`CIPD_HTTP_USER_AGENT_PREFIX={user_agent}/manual {client} "
+            "selfupdate -version-file '{version_file}'` "
+            "to diagnose if this is persistent.".format(
+                user_agent=user_agent(), client=CLIENT, version_file=VERSION_FILE,
+            ),
+            file=sys.stderr,
+        )
+        raise
 
 
-if __name__ == '__main__':
-  init()
-  subprocess.check_call([CLIENT] + sys.argv[1:])
+if __name__ == "__main__":
+    init()
+    subprocess.check_call([CLIENT] + sys.argv[1:])