* added lxml end-to-end test

* configured test logging

* prefer /usr/bin/timeout

* added debug logging

* added pdf end to end preprocessing test

* fixed serialization error

* added debug logging

* check pipeline results

* test png output

* fixed element type check

* install poppler-utils into docker image

* add --assume-yes

Bumps [tensorflow-transform](https://github.com/tensorflow/transform) from 0.21.0 to 0.25.0.
- [Release notes](https://github.com/tensorflow/transform/releases)
- [Changelog](https://github.com/tensorflow/transform/blob/master/RELEASE.md)
- [Commits](https://github.com/tensorflow/transform/compare/v0.21.0...v0.25.0

)

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Bumps [tqdm](https://github.com/tqdm/tqdm) from 4.49.0 to 4.50.0.
- [Release notes](https://github.com/tqdm/tqdm/releases)
- [Commits](https://github.com/tqdm/tqdm/compare/v4.49.0...v4.50.0

)

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Bumps [pytest](https://github.com/pytest-dev/pytest) from 6.0.2 to 6.1.0.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/pytest-dev/pytest/compare/6.0.2...6.1.0

)

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Bumps [sciencebeam-utils](https://github.com/elifesciences/sciencebeam-utils) from 0.1.0 to 0.1.1.
- [Release notes](https://github.com/elifesciences/sciencebeam-utils/releases)
- [Commits](https://github.com/elifesciences/sciencebeam-utils/compare/v0.1.0...v0.1.1

)

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Bumps [tensorflow](https://github.com/tensorflow/tensorflow) from 1.15.3 to 1.15.4.
- [Release notes](https://github.com/tensorflow/tensorflow/releases)
- [Changelog](https://github.com/tensorflow/tensorflow/blob/master/RELEASE.md)
- [Commits](https://github.com/tensorflow/tensorflow/compare/v1.15.3...v1.15.4

)

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