Merge pull request #3762 from vmarkovtsev/patch-1

MNT : WebAgg: flush stdout after printing, redirect "stopped" message to stder
Fix for #3789, segfault in _tri
Fix #3790. Correctly scale quadmesh linewidth to dpi in Agg backend.
Merge pull request #3793 from mdboom/quadmesh_linewidth

Correctly scale quadmesh linewidth to dpi
Merge pull request #3797 from ianthomas23/3789_segfault

Fix for #3789, segfault in _tri
Merge remote-tracking branch 'upstream/v1.4.x'

Conflicts:
	src/_backend_agg.cpp
Update test image for slight difference in calculation between 1.4.x and master
BLD: Modified mocksip to allow for building the docs without qt being
installed
STY: pep8 fixes
Instantiate Sip Mock before use
fix trailing whitespace
fix multiple whitespace issues in svg_*.py examples (E293, E291)
pep8 fix E201
pep8 fix e2* in examples dir part 1/2
pep8 fix e2* in examples dir part 2/2

Signed-off-by: Thomas Hisch <t.hisch@gmail.com>
pep8 fix E701
pep8 fix E502 (redundant backslash)
pep8 fix e702,e703
pep8 fix E302
remove blacklisted examples from coding style unittest

Signed-off-by: Thomas Hisch <t.hisch@gmail.com>