René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"different behaviour between 3.3.0 and 3.2.2 (and earlier) for plotting in a Tk canvas","articleBody":"### Bug report\r\nI am trying to plot graphs in a Tk canvas, and I find different behavior for mpl 3.3.0 and 3.2.2.\r\nI am running the same code: \r\n\r\nThe code I am reusing it from here: https://github.com/SuperMechaDeathChrist/Widgets/blob/master/plt_figure_w_controls.py \r\n\r\nit runs well for 3.2.2 and bellow but get the following error for 3.3.0:\r\n```python\r\nTraceback (most recent call last):\r\n  File \"/home/yr2369/dev/mosydb/_personal/tests/plt_sg.py\", line 90, in \u003cmodule\u003e\r\n    'fig_cv').TKCanvas, fig, window.FindElement('controls_cv').TKCanvas)\r\n  File \"/home/yr2369/dev/mosydb/_personal/tests/plt_sg.py\", line 17, in draw_figure_w_toolbar\r\n    toolbar = Toolbar(figure_canvas_agg, canvas_toolbar)\r\n  File \"/home/yr2369/dev/mosydb/_personal/tests/plt_sg.py\", line 34, in __init__\r\n    super(Toolbar, self).__init__(*args, **kwargs)\r\n  File \"/home/yr2369/anaconda3/envs/mosydb/lib/python3.7/site-packages/matplotlib/backends/_backend_tk.py\", line 525, in __init__\r\n    NavigationToolbar2.__init__(self, canvas)\r\n  File \"/home/yr2369/anaconda3/envs/mosydb/lib/python3.7/site-packages/matplotlib/backend_bases.py\", line 2866, in __init__\r\n    self.set_history_buttons()\r\n  File \"/home/yr2369/anaconda3/envs/mosydb/lib/python3.7/site-packages/matplotlib/backends/_backend_tk.py\", line 640, in set_history_buttons\r\n    self._buttons['Back']['state'] = tk.DISABLED\r\nKeyError: 'Back'\r\n\r\nProcess finished with exit code 1\r\n```\r\nIt looks like an easy fix, but maybe I am wrong - let me know what additional details you need from me. \r\nI use python 3.7.8\r\nps - to test the code -` pip install pysimplegui`\r\n\r\nThank you","author":{"url":"https://github.com/yevgenyr","@type":"Person","name":"yevgenyr"},"datePublished":"2020-08-12T18:58:59.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/18232/matplotlib/issues/18232"}