loading TCL / Tk symbols dynamically

.travis.yml

@@ -123,6 +123,8 @@ script:
   # Travis VM to run out of memory (since so many copies of inkscape and
   # ghostscript are running at the same time).
   - |
+    echo Testing import of tkagg backend
+    MPLBACKEND="tkagg" python -c 'import matplotlib.pyplot as plt; print(plt.get_backend())'
     echo Testing using $NPROC processes
     echo The following args are passed to nose $NOSE_ARGS
     if [[ $BUILD_DOCS == false ]]; then

appveyor.yml

@@ -87,6 +87,8 @@ install:
 test_script:
   # Now build the thing..
   - '%CMD_IN_ENV% python setup.py develop'
+  # Test import of tkagg backend
+  - python -c "import matplotlib as m; m.use('tkagg'); import matplotlib.pyplot as plt; print(plt.get_backend())"
   # tests
   - python tests.py
   # remove to get around libpng issue?