Revert to single-line command for doctr invocation.

[pp-mo]

Another go at fixing #3542
Since #3577 seems to have been bugged.

[lbdreyer]

It seems strange the > doesn't work.
Have you tested that this line would now work?

[pp-mo]

The ">" form seems to leave newlines in it (or possibly carriage-returns, if there is a line-end problem??).
So testing with the yaml package, I get...

>>> with open('.travis.yml') as fo:
...   data = yaml.safe_load(fo)
... 
>>> print(data['script'][-1])
if [[ "${ORG}" == 'SciTools' && "${TRAVIS_EVENT_TYPE}" == 'push' && "${PUSH_BUILT_DOCS}" == 'true' ]]; then
  cd ${INSTALL_DIR};
  pip install doctr;
  doctr deploy --deploy-repo SciTools-docs/iris --built-docs docs/iris/build/html
    --key-path .github/deploy_key.scitools-docs.enc
    --no-require-master
    ${TRAVIS_BRANCH:-${TRAVIS_TAG}};
fi

>>> # definitely newlines ...
>>> print(repr(data['script'][-1]))
'if [[ "${ORG}" == \'SciTools\' && "${TRAVIS_EVENT_TYPE}" == \'push\' && "${PUSH_BUILT_DOCS}" == \'true\' ]]; then\n  cd ${INSTALL_DIR};\n  pip install doctr;\n  doctr deploy --deploy-repo SciTools-docs/iris --built-docs docs/iris/build/html\n    --key-path .github/deploy_key.scitools-docs.enc\n    --no-require-master\n    ${TRAVIS_BRANCH:-${TRAVIS_TAG}};\nfi\n'
>>> 

I don't really get this. The ">" form is supposed to "fold" lines + remove newlines, but here we definitely got embedded newlines.

[pp-mo]

Have you tested that this line would now work?

No. It's hard to do unless it's running in the right repository.
In principle, merging to a feature branch might work (which is what Scitools/iris/pushdocs_test was for). I may try that ...

[pp-mo]

Hi @lbdreyer
Restarted build, which crashed for some reason?

Tested on separate "feature" branch : it works at last !! 🚀
See 'pushdocs_trial' branch docs here