Log Message:
py-nbconvert: updated to 5.6.0

5.6.0:
Significant Changes

Jupter Client Pin
The jupyter_client dependency is now pinned to >5.3.1. This is done to \ 
support the Parallel NBConvert below, and future versions may require interface \ 
changes from that version.

Parallel NBConvert
NBConvert --execute can now be run in parallel via threads, multiprocessing, or \ 
async patterns! This means you can now parallelize nbconvert via a bash loop, or \ 
a python concurrency pattern and it should be able to execute those notebooks in \ 
parallel.

Kernels have varying support for safe concurrent execution. The ipython kernel \ 
(ipykernel version 1.5.2 and higher) should be safe to run concurrently using \ 
Python 3. However, the Python 2 ipykernel does not always provide safe \ 
concurrent execution and sometimes fails with a socket bind exception. Unlike \ 
ipykernel which is maintained by the project, other community-maintained kernels \ 
may have varying support for concurrent execution, and these kernels were not \ 
tested heavily.

Issues for nbconvert can be viewed here:
.. note: We'll keep an eye for issues related to this new capability and try to \ 
quickly patch any discovered issues post release. The improvement required \ 
touching three projects with separate releases, so if you do find an issue try \ 
upgrading dependencies and listing your dependencies for your environment when \ 
reporting.

Execute Loop Rewrite
This release completely rewrote the execution loop responsible for monitoring \ 
kernel messages until cell execution is completed. This removes an error where \ 
kernel messages could be dropped if too many were posted too quickly. \ 
Furthermore, the change means that messages are not buffered. Now, messages can \ 
be logged immediately rather than waiting for the cell to terminate.

Comprehensive notes

New Features
- Make a default global location for custom user templates
- Parallel execution improvements
- Added store_history option to preprocess_cell and run_cell
- Simplify the function signature for preprocess()
- Set flag to not always stop kernel execution on errors
- setup_preprocessor passes kwargs to start_new_kernel

Fixing Problems
- Very fast stream outputs no longer drop some messages
- LaTeX errors now properly raise exceptions
- Improve template whitespacing
- Fixes for character in LaTeX exports and filters
- Mistune pinned in preparation for 2.0 release
- Require mock only on Python 2
- Fix selection of mimetype when converting to HTML
- Correct a few typos
- Update export_from_notebook names
- Dedenting html in ExtractOutputPreprocessor
- Fix backwards incompatibility with markdown2html
- Fixed html image tagging
- Remove unnecessary css

Testing, Docs, and Builds
- Pip-install nbconvert on readthedocs.org
- Fix various doc build issues
- Add issue templates
- Added instructions for bumping the version forward when releasing
- Fix Testing on Windows
- Refactored test_run_notebooks
- Fixed documentation typos