Fix textbox cursor color, set its linewidth.

The cursor used to be black but the default of vlines color now matches
`rcParams["lines.color"]` (blue), so change that back to black.  Setting
the linewidth to 1 also looks a bit nicer (than the thicker default
linewidth).

Author: anntzer

lib/matplotlib/widgets.py

@@ -1029,7 +1029,7 @@ def __init__(self, ax, label, initial='',
 
         self.cursor_index = 0
 
-        self.cursor = ax.vlines(0, 0, 0, visible=False,
+        self.cursor = ax.vlines(0, 0, 0, visible=False, color="k", lw=1,
                                 transform=mpl.transforms.IdentityTransform())
 
         self.connect_event('button_press_event', self._click)