JSON tidying and two issues

[ximenesuk]

This PR includes

• some JSON tidying:
  • 8cb69ea1 use the full headers
  • 369ee838 split the log into a summary message and results (rest of log)
• address the two issues:

  • 15

  • 16 (with updated/added tests)

• and some intermediate flake8 fixes

To test, use docs endpoint to confirm correct JSON for validate. See separate issues for testing of those.

[volcan01010]

• Multi-convert described in bug gives 1 file and correct log
• JSON gives named attributes and separate "message" and errors
• Unicode error gives the line number.