Merge pull request matplotlib#20233 from QuLogic/ubuntu20

Add a Ubuntu 20.04 / Python 3.9 CI run

Author: timhoffm

.github/workflows/tests.yml

@@ -37,6 +37,10 @@ jobs:
             python-version: 3.8
             extra-requirements: '-r requirements/testing/extra.txt'
             XVFB_RUN: xvfb-run -a
+          - os: ubuntu-20.04
+            python-version: 3.9
+            extra-requirements: '-r requirements/testing/extra.txt'
+            XVFB_RUN: xvfb-run -a
           - os: macos-latest
             python-version: 3.8
             XVFB_RUN: ""
@@ -176,7 +180,7 @@ jobs:
                echo 'PySide2 is not available'
           fi
           python -m pip install --upgrade \
-            -f https://extras.wxpython.org/wxPython4/extras/linux/gtk3/ubuntu-18.04 \
+            -f https://extras.wxpython.org/wxPython4/extras/linux/gtk3/ubuntu-$(lsb_release -r -s) \
             wxPython &&
             python -c 'import wx' &&
             echo 'wxPython is available' ||
@@ -190,7 +194,11 @@ jobs:
           # Set flag in a delayed manner to avoid issues with installing other
           # packages
           if [[ "${{ runner.os }}" != 'macOS' ]]; then
-            export CPPFLAGS=--coverage
+            if [[ "$(lsb_release -r -s)" == "20.04" ]]; then
+              export CPPFLAGS='--coverage -fprofile-abs-path'
+            else
+              export CPPFLAGS='--coverage'
+            fi
           fi
 
           # All dependencies must have been pre-installed, so that the minver

lib/matplotlib/tests/baseline_images/test_backend_pgf/pgf_pdflatex.pdf

@@ -87,11 +87,18 @@ def test_xelatex():
     create_figure()
 
 
+try:
+    _old_gs_version = mpl._get_executable_info('gs').version < '9.50'
+except mpl.ExecutableNotFoundError:
+    _old_gs_version = True
+
+
 # test compiling a figure to pdf with pdflatex
 @needs_pdflatex
 @pytest.mark.skipif(not _has_tex_package('ucs'), reason='needs ucs.sty')
 @pytest.mark.backend('pgf')
-@image_comparison(['pgf_pdflatex.pdf'], style='default')
+@image_comparison(['pgf_pdflatex.pdf'], style='default',
+                  tol=11.7 if _old_gs_version else 0)
 def test_pdflatex():
     if os.environ.get('APPVEYOR'):
         pytest.xfail("pdflatex test does not work on appveyor due to missing "
@@ -127,15 +134,15 @@ def test_rcupdate():
                 'pgf.preamble': ('\\usepackage[utf8x]{inputenc}'
                                  '\\usepackage[T1]{fontenc}'
                                  '\\usepackage{sfmath}')}]
-    tol = [6, 0]
+    tol = [0, 13.2] if _old_gs_version else [0, 0]
     for i, rc_set in enumerate(rc_sets):
         with mpl.rc_context(rc_set):
             for substring, pkg in [('sfmath', 'sfmath'), ('utf8x', 'ucs')]:
                 if (substring in mpl.rcParams['pgf.preamble']
                         and not _has_tex_package(pkg)):
                     pytest.skip(f'needs {pkg}.sty')
             create_figure()
-            compare_figure('pgf_rcupdate%d.pdf' % (i + 1), tol=tol[i])
+            compare_figure(f'pgf_rcupdate{i + 1}.pdf', tol=tol[i])
 
 
 # test backend-side clipping, since large numbers are not supported by TeX