scancode license scan produces invalid yaml

[AyanSinhaMahapatra]

Description

Please leave a brief description of the bug or feature request:

scancode license scan now has license references by default, and as license texts
often has whitespace to the left, this leads to invalid yaml output when --license
option is used.

How To Reproduce

Tell us how to reproduce the issue.

From scancode latest develop:

./configure --clean && ./configure --dev
scancode -clipeu --classify --summary samples --yaml output.yaml
python
> import saneyaml
> path = "path/to/output.yaml"
>  data = saneyaml.load(open(path).read())

This results in:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/ayansinha/nexB/write_access/scancode-toolkit/venv/lib/python3.8/site-packages/saneyaml.py", line 62, in load
    return yaml.load(s, Loader=loader)
  File "/home/ayansinha/nexB/write_access/scancode-toolkit/venv/lib/python3.8/site-packages/yaml/__init__.py", line 81, in load
    return loader.get_single_data()
  File "/home/ayansinha/nexB/write_access/scancode-toolkit/venv/lib/python3.8/site-packages/yaml/constructor.py", line 49, in get_single_data
    node = self.get_single_node()
  File "yaml/_yaml.pyx", line 673, in yaml._yaml.CParser.get_single_node
  File "yaml/_yaml.pyx", line 687, in yaml._yaml.CParser._compose_document
  File "yaml/_yaml.pyx", line 731, in yaml._yaml.CParser._compose_node
  File "yaml/_yaml.pyx", line 845, in yaml._yaml.CParser._compose_mapping_node
  File "yaml/_yaml.pyx", line 729, in yaml._yaml.CParser._compose_node
  File "yaml/_yaml.pyx", line 806, in yaml._yaml.CParser._compose_sequence_node
  File "yaml/_yaml.pyx", line 731, in yaml._yaml.CParser._compose_node
  File "yaml/_yaml.pyx", line 847, in yaml._yaml.CParser._compose_mapping_node
  File "yaml/_yaml.pyx", line 860, in yaml._yaml.CParser._parse_next_event
yaml.parser.ParserError: while parsing a block mapping
  in "<unicode string>", line 561, column 9
did not find expected key
  in "<unicode string>", line 600, column 40

System configuration

For bug reports, it really helps us to know:

• What OS are you running on? (Windows/MacOS/Linux) ubuntu 20.04
• What version of scancode-toolkit was used to generate the scan file? 32.0.0rc1
• What installation method was used to install/run scancode? (pip/source download/other) source checkout

[AyanSinhaMahapatra]

This also happens with the --license-text option enabled, which adds the attribute matched_text.

[AyanSinhaMahapatra]

See error reproduced here: https://dev.azure.com/nexB/scancode-toolkit/_build/results?buildId=9752&view=logs&j=1412dbfa-421a-5a40-8ddf-7073fc46aa19&t=13c90161-2109-5957-f563-a96fefc7d869&l=6316

[AyanSinhaMahapatra]

See #3220 (comment)