Backport PR #651 on branch 2.1 (Update error messages for mpl and mpl_animators)

changelog/651.trivial.rst

@@ -0,0 +1 @@
+Updated the error messages when missing either ``matplotlib`` or ``mpl_animators`` when creating a plot.

ndcube/visualization/descriptor.py

@@ -1,7 +1,11 @@
 import functools
 
-MISSING_MATPLOTLIB_ERROR_MSG = ("Matplotlib can not be imported, so the default plotting "
-                                "functionality is disabled. Please install matplotlib.")
+MISSING_MATPLOTLIB_ERROR_MSG = ("matplotlib cannot be imported, so the default plotting "
+                                "functionality is disabled. Please install matplotlib")
+MISSING_ANIMATORS_ERROR_MSG = ("mpl_animators cannot be imported, so the default plotting "
+                               "functionality is disabled. Please install mpl_animators")
+
+__all__ = ['PlotterDescriptor', 'MISSING_MATPLOTLIB_ERROR_MSG', 'MISSING_ANIMATORS_ERROR_MSG']
 
 
 class PlotterDescriptor:
@@ -29,16 +33,20 @@ def _resolve_default_type(self, raise_error=True):
         # delay the import of matplotlib until the plotter is first
         # accessed.
         if self._default_type in ("mpl_plotter", "mpl_sequence_plotter"):
-            try:
-                if self._default_type == "mpl_plotter":
+            if self._default_type == "mpl_plotter":
+                try:
                     from ndcube.visualization.mpl_plotter import MatplotlibPlotter
                     return MatplotlibPlotter
-                elif self._default_type == "mpl_sequence_plotter":
+                except ImportError as e:
+                    if raise_error:
+                        raise ImportError(MISSING_MATPLOTLIB_ERROR_MSG) from e
+            elif self._default_type == "mpl_sequence_plotter":
+                try:
                     from ndcube.visualization.mpl_sequence_plotter import MatplotlibSequencePlotter
                     return MatplotlibSequencePlotter
-            except ImportError as e:
-                if raise_error:
-                    raise ImportError(MISSING_MATPLOTLIB_ERROR_MSG) from e
+                except ImportError as e:
+                    if raise_error:
+                        raise ImportError(MISSING_ANIMATORS_ERROR_MSG) from e
 
         elif self._default_type is not None:
             return self._default_type

ndcube/visualization/mpl_plotter.py

@@ -5,10 +5,10 @@
 import numpy as np
 from astropy.utils.exceptions import AstropyUserWarning
 from astropy.visualization.wcsaxes import WCSAxes
-from mpl_animators import ArrayAnimatorWCS
 
 from . import plotting_utils as utils
 from .base import BasePlotter
+from .descriptor import MISSING_ANIMATORS_ERROR_MSG
 
 __all__ = ['MatplotlibPlotter']
 
@@ -189,9 +189,15 @@ def _plot_2D_cube(self, wcs, axes=None, plot_axes=None, axes_coordinates=None,
 
     def _animate_cube(self, wcs, plot_axes=None, axes_coordinates=None,
                       axes_units=None, data_unit=None, **kwargs):
+        try:
+            from mpl_animators import ArrayAnimatorWCS
+        except ImportError as e:
+            raise ImportError(MISSING_ANIMATORS_ERROR_MSG) from e
+
         # Derive inputs for animation object and instantiate.
         data, wcs, plot_axes, coord_params = self._prep_animate_args(wcs, plot_axes,
                                                                      axes_units, data_unit)
+
         ax = ArrayAnimatorWCS(data, wcs, plot_axes, coord_params=coord_params, **kwargs)
 
         # We need to modify the visible axes after the axes object has been created.