Digging into the production logs of the npm loader, the following errors are reported:
```
Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/swh/loader/core/loader.py", line 895, in load
more_data_to_fetch = self.fetch_data()
File "/usr/lib/python3/dist-packages/swh/loader/npm/loader.py", line 203, in fetch_data
data = next(self.new_versions)
File "/usr/lib/python3/dist-packages/swh/loader/npm/client.py", line 149, in prepare_package_versions
version_data)
File "/usr/lib/python3/dist-packages/swh/loader/npm/client.py", line 210, in _prepare_package_version
author = extract_npm_package_author(package_json)
File "/usr/lib/python3/dist-packages/swh/loader/npm/utils.py", line 95, in extract_npm_package_author
author_data = parse_npm_package_author(author_str)
File "/usr/lib/python3/dist-packages/swh/loader/npm/utils.py", line 52, in parse_npm_package_author
author_str.replace('<>', '').replace('()', ''),
AttributeError: 'list' object has no attribute 'replace'
```
```
Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/swh/loader/core/loader.py", line 895, in load
more_data_to_fetch = self.fetch_data()
File "/usr/lib/python3/dist-packages/swh/loader/npm/loader.py", line 203, in fetch_data
data = next(self.new_versions)
File "/usr/lib/python3/dist-packages/swh/loader/npm/client.py", line 149, in prepare_package_versions
version_data)
File "/usr/lib/python3/dist-packages/swh/loader/npm/client.py", line 210, in _prepare_package_version
author = extract_npm_package_author(package_json)
File "/usr/lib/python3/dist-packages/swh/loader/npm/utils.py", line 97, in extract_npm_package_author
author_str = _author_str(package_json['authors'][0])
KeyError: 0
```
The first error happens when the `author` field in a `package.json` file corresponds to a list instead of a string,
while the second one happens when the `author` field corresponds to a dict instead of a string,