Disable pylint import checks for distutils

Pylint complains about distutils import in virtualenv (tox):
pylint-dev/pylint#73
```
E: 22, 0: No name 'version' in module 'distutils' (no-name-in-module)
E: 22, 0: Unable to import 'distutils.version.StrictVersion' (import-error)
```

Add inline pylint disable for `no-name-in-module` and
`import-error` checks as workaround for this issue.

securesystemslib/gpg/util.py

@@ -19,7 +19,8 @@
 import subprocess
 import shlex
 import re
-from distutils.version import StrictVersion
+
+from distutils.version import StrictVersion # pylint: disable=no-name-in-module,import-error
 
 import cryptography.hazmat.backends as backends
 import cryptography.hazmat.primitives.hashes as hashing