Failure during Ubuntu importer run

I got these failures:
```
Importing data from ubuntu
Failed to get updated_advisories: with {'type': 'deb', 'namespace': 'ubuntu'}:
Traceback (most recent call last):
File "/home/pombreda/w421/vulnerablecode/vulnerabilities/data_source.py", line 481, in updated_advisories
oval_data = self.get_data_from_xml_doc(oval_file, metadata)
File "/home/pombreda/w421/vulnerablecode/vulnerabilities/data_source.py", line 538, in get_data_from_xml_doc
affected_version_range = VersionSpecifier.from_scheme_version_spec_string(
File "/home/pombreda/w421/vulnerablecode/venv/lib/python3.8/site-packages/univers/version_specifier.py", line 137, in from_scheme_version_spec_string
rng = VersionRange(version_range, scheme)
File "/home/pombreda/w421/vulnerablecode/venv/lib/python3.8/site-packages/univers/version_range.py", line 42, in __init__
self.version = version_class(self.version)
File "/home/pombreda/w421/vulnerablecode/venv/lib/python3.8/site-packages/univers/versions.py", line 152, in __init__
object.__setattr__(self, "value", _DebianVersion.from_string(version_string))
File "/home/pombreda/w421/vulnerablecode/venv/lib/python3.8/site-packages/univers/debian.py", line 130, in from_string
raise ValueError('Invalid version string: "{}"'.format(version))
ValueError: Invalid version string: "1:1.12_1.12.6-1+deb9u1build0.18.04.1"

Failed to get updated_advisories: with {'type': 'deb', 'namespace': 'ubuntu'}:
Traceback (most recent call last):
File "/home/pombreda/w421/vulnerablecode/vulnerabilities/data_source.py", line 481, in updated_advisories
oval_data = self.get_data_from_xml_doc(oval_file, metadata)
File "/home/pombreda/w421/vulnerablecode/vulnerabilities/data_source.py", line 569, in get_data_from_xml_doc
Advisory(
File "", line 7, in __init__
File "/home/pombreda/w421/vulnerablecode/vulnerabilities/data_source.py", line 96, in __post_init__
raise ValueError("CVE expected, found: {}".format(self.vulnerability_id))
ValueError: CVE expected, found: CVE-2013-NNN1 on Ubuntu 14.04 LTS (trusty) - low.
```
there are a few issues there:
1. it is failing
2. worse, I cannot diagnose what, where and why this failed

See also https://github.com/nexB/univers/issues/6