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Description of problem:

On RHEL 7.6, both on x86_64 as on ppc64le, using 'title' commands
in Matplotlib issues a warning/error 

           'Unable to parse the pattern'

On RHEL 7.5, and for that matter, any recent Fedora
it does NOT give this spurious message.

Version-Release number of selected component (if applicable):

python-matplotlib-1.2.0-15.el7.x86_64

This package has not been updated 7.5 -> 7.6,
So it must be in dependencies...

How reproducible:

Always.

Steps to Reproduce:
1. Run e.g this:
   #! /bin/python
   import matplotlib.pyplot as plt
   plt.title('Beren!')
   plt.show()

Actual results:

The plot succeeds, but a line
'Unable to parse the pattern' is printed to stderr.

Expected results:

No spurious message.

Additional info:

Smells like something font-related.

The guilty part seems to be 'freetype'.  Downgrading it (and its dependencies)
to the 7.5 versions, solves the problem.

See https://bugzilla.redhat.com/show_bug.cgi?id=1653706

That message should be came from either commands of fontconfig such as fc-match/fc-list/fc-pattern though, strictly speaking this isn't a regression at all. because this was added for valid error check. thus, this is a potential bug in something calls those commands. see https://gitlab.freedesktop.org/fontconfig/fontconfig/commit/604c2a683f1357fc65bad372b5d25a90099f827f

Querying the size in the name such as "large" is wrong. fontconfig doesn't support that. that should be converted to the number.

Created attachment 1522635 [details]
Make font manager ignore Key Errors for bad-fonts patch

Created attachment 1522636 [details]
Skip over broken TTF fonts when creating cache

Created attachment 1522637 [details]
Fix for Python3

Created attachment 1522639 [details]
Fix catch ValueError

Created attachment 1522640 [details]
Remove call to nonexistent FT"Font get fontsize

ASSIGNED:

"Unable to parse the pattern" is still present during t.py execution. (For reproducer see comment 16)

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2019:2203