Remove except ImportError's

clean_registry.py

 import sys
 import tarfile
 import subprocess
+import yaml
+import docker
 
 from argparse import ArgumentParser
 from distutils.version import LooseVersion
 from requests import exceptions
 from docker.errors import APIError, NotFound, TLSParameterError
 
-try:
-    import docker
-except ImportError:
-    error("Please install docker-py with: pip3 install docker")
-
-try:
-    import yaml
-except ImportError:
-    error("Please install PyYaml with: pip3 install pyyaml")
-
 VERSION = "1.2"
 REGISTRY_DIR = "REGISTRY_STORAGE_FILESYSTEM_ROOTREGISTRY_DIR"