vulnerabilities.importers.nvd.NVDImporter - gzip.BadGzipFile

https://github.com/nexB/vulnerablecode/blob/59406a5221d277f25a4b87a6203f07ec4853958a/vulnerabilities/importers/nvd.py#L49

Attempting to run the vulnerabilities.importers.nvd.NVDImporter importer results in:

```
Failed to run importer vulnerabilities.importers.nvd.NVDImporter. Continuing...
File "/app/vulnerabilities/management/commands/import.py", line 62, in import_data
ImportRunner(importer).run()
File "/app/vulnerabilities/import_runner.py", line 44, in run
count = process_advisories(advisory_datas=advisory_datas, importer_name=importer_name)
File "/app/vulnerabilities/import_runner.py", line 54, in process_advisories
for data in advisory_datas:
File "/app/vulnerabilities/importers/nvd.py", line 42, in advisory_data
data = fetch(download_url)
File "/app/vulnerabilities/importers/nvd.py", line 49, in fetch
data = gzip.decompress(gz_file.content)
File "/usr/local/lib/python3.9/gzip.py", line 556, in decompress
return f.read()
File "/usr/local/lib/python3.9/gzip.py", line 300, in read
return self._buffer.read(size)
File "/usr/local/lib/python3.9/gzip.py", line 487, in read
if not self._read_gzip_header():
File "/usr/local/lib/python3.9/gzip.py", line 435, in _read_gzip_header
raise BadGzipFile('Not a gzipped file (%r)' % magic)
gzip.BadGzipFile: Not a gzipped file (b'