Fix matplotlib import error

Framework/PythonInterface/mantid/plots/utility.py

@@ -14,7 +14,7 @@ from enum import Enum
 
 # 3rd party imports
 from matplotlib.legend import Legend
-from matplotlib import cm, pyplot as plt, __version__ as mpl_version_str
+from matplotlib import cm, __version__ as mpl_version_str
 from matplotlib.container import ErrorbarContainer
 
 # -----------------------------------------------------------------------------
@@ -215,7 +215,7 @@ def get_single_workspace_log_value(ws_index, *, log_values=None, matrix_ws=None,
 
 def colormap_as_plot_color(number_colors: int, colormap_name: str = 'viridis', cmap=None):
     if not cmap:
-        cmap = plt.get_cmap(name=colormap_name)
+        cmap = cm.get_cmap(name=colormap_name)
 
     for i in range(number_colors):
         yield cmap(float(i) / number_colors)