Require python3-click-plugins
    
    gr_modtool appears to use python3-click for command line
    processing. If python3-click or python3-click-plugins are not
    installed, I get the following tracebacks. python3-click-plugins
    Requires python3-click, so it's sufficient to Require the former.
    
    [root@69f00c035e8c /]# gr_modtool --help
    Traceback (most recent call last):
      File "/usr/bin/gr_modtool", line 25, in <module>
        from gnuradio.modtool.cli.base import cli
      File "/usr/lib64/python3.8/site-packages/gnuradio/modtool/cli/__init__.py", line 26, in <module>
        from .base import cli, common_params, block_name, ModToolException
      File "/usr/lib64/python3.8/site-packages/gnuradio/modtool/cli/base.py", line 35, in <module>
        import click
    ModuleNotFoundError: No module named 'click'
    
    [root@69f00c035e8c /]# gr_modtool --help
    Traceback (most recent call last):
      File "/usr/bin/gr_modtool", line 25, in <module>
        from gnuradio.modtool.cli.base import cli
      File "/usr/lib64/python3.8/site-packages/gnuradio/modtool/cli/__init__.py", line 26, in <module>
        from .base import cli, common_params, block_name, ModToolException
      File "/usr/lib64/python3.8/site-packages/gnuradio/modtool/cli/base.py", line 37, in <module>
        from click_plugins import with_plugins
    ModuleNotFoundError: No module named 'click_plugins'