diff --git a/mne/conftest.py b/mne/conftest.py
index c9c8d1160b5..89a275e362b 100644
--- a/mne/conftest.py
+++ b/mne/conftest.py
@@ -3,6 +3,8 @@
 #
 # License: BSD (3-clause)
 
+from distutils.version import LooseVersion
+import gc
 import os
 import os.path as op
 import shutil
@@ -79,6 +81,7 @@ def pytest_configure(config):
     ignore:The sklearn.*module.*deprecated.*:FutureWarning
     ignore:.*TraitTuple.*trait.*handler.*deprecated.*:DeprecationWarning
     ignore:.*rich_compare.*metadata.*deprecated.*:DeprecationWarning
+    ignore:.*In future, it will be an error for 'np.bool_'.*:DeprecationWarning
     always:.*get_data.* is deprecated in favor of.*:DeprecationWarning
     """  # noqa: E501
     for warning_line in warning_lines.split('\n'):
@@ -91,6 +94,7 @@ def pytest_configure(config):
 def matplotlib_config():
     """Configure matplotlib for viz tests."""
     import matplotlib
+    from matplotlib import cbook
     # "force" should not really be necessary but should not hurt
     kwargs = dict()
     with warnings.catch_warnings(record=True):  # ignore warning
@@ -110,6 +114,18 @@ def matplotlib_config():
     else:
         ETSConfig.toolkit = 'qt4'
 
+    # Make sure that we always reraise exceptions in handlers
+    orig = cbook.CallbackRegistry
+
+    class CallbackRegistryReraise(orig):
+        def __init__(self, exception_handler=None):
+            args = ()
+            if LooseVersion(matplotlib.__version__) >= LooseVersion('2.1'):
+                args += (exception_handler,)
+            super(CallbackRegistryReraise, self).__init__(*args)
+
+    cbook.CallbackRegistry = CallbackRegistryReraise
+
 
 @pytest.fixture()
 def check_gui_ci():
@@ -201,7 +217,7 @@ def backend_name(request):
 
 
 @pytest.yield_fixture
-def renderer(backend_name):
+def renderer(backend_name, garbage_collect):
     """Yield the 3D backends."""
     from mne.viz.backends.renderer import _use_test_3d_backend
     _check_skip_backend(backend_name)
@@ -211,6 +227,13 @@ def renderer(backend_name):
         renderer._close_all()
 
 
+@pytest.yield_fixture
+def garbage_collect():
+    """Garbage collect on exit."""
+    yield
+    gc.collect()
+
+
 @pytest.fixture(scope="module", params=[
     "pyvista",
 ])
diff --git a/mne/io/nirx/nirx.py b/mne/io/nirx/nirx.py
index 3abb986dd7e..f7a8ec123d9 100644
--- a/mne/io/nirx/nirx.py
+++ b/mne/io/nirx/nirx.py
@@ -78,8 +78,9 @@ def __init__(self, fname, preload=False, verbose=None):
 
         # Read number of rows/samples of wavelength data
         last_sample = -1
-        for line in _open(files['wl1']):
-            last_sample += 1
+        with _open(files['wl1']) as fid:
+            for line in fid:
+                last_sample += 1
 
         # Read participant information file
         inf = ConfigParser(allow_no_value=True)
diff --git a/mne/viz/tests/test_3d.py b/mne/viz/tests/test_3d.py
index 11cfbc4c501..40d51cffd07 100644
--- a/mne/viz/tests/test_3d.py
+++ b/mne/viz/tests/test_3d.py
@@ -639,7 +639,7 @@ def test_plot_volume_source_estimates_morph():
 @requires_pysurfer
 @requires_mayavi
 @traits_test
-def test_plot_vector_source_estimates():
+def test_plot_vector_source_estimates(garbage_collect):
     """Test plotting of vector source estimates."""
     sample_src = read_source_spaces(src_fname)
 
@@ -721,7 +721,7 @@ def test_brain_colorbar(orientation, diverging, lims):
 @requires_pysurfer
 @testing.requires_testing_data
 @traits_test
-def test_mixed_sources_plot_surface():
+def test_mixed_sources_plot_surface(garbage_collect):
     """Test plot_surface() for  mixed source space."""
     src = read_source_spaces(fwd_fname2)
     N = np.sum([s['nuse'] for s in src])  # number of sources
diff --git a/mne/viz/utils.py b/mne/viz/utils.py
index de23bf0dc8c..5cbf6199384 100644
--- a/mne/viz/utils.py
+++ b/mne/viz/utils.py
@@ -1974,7 +1974,7 @@ def key_press(self, event):
         elif self.index >= len(self.cycle):
             self.index = 0
         cmap = self.cycle[self.index]
-        self.cbar.set_cmap(cmap)
+        self.cbar.mappable.set_cmap(cmap)
         self.cbar.draw_all()
         self.mappable.set_cmap(cmap)
         self.mappable.set_norm(self.cbar.norm)
diff --git a/requirements.txt b/requirements.txt
index 413684d8991..21a56e19de4 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,7 +1,6 @@
 numpy
 scipy
 matplotlib
-mayavi
 pyqt5!=5.14.1
 pyqt5-sip
 sip
@@ -23,11 +22,12 @@ joblib
 psutil
 dipy
 https://api.github.com/repos/numpy/numpydoc/zipball/master
+mayavi
 PySurfer[save_movie]
 nilearn
 neo
 xlrd
 pydocstyle
 flake8
-https://github.com/mcmtroffaes/sphinxcontrib-bibtex/zipball/29694f215b39d64a31b845aafd9ff2ae9329494f
+https://api.github.com/repos/mcmtroffaes/sphinxcontrib-bibtex/zipball/29694f215b39d64a31b845aafd9ff2ae9329494f
 pyvista>=0.23.1