Integration test harness can produce a distro with illegal name due to trailing underscore

[arcivanov]

First detected in: https://github.com/pybuilder/pybuilder/runs/3580679357?check_suite_focus=true

         summaries.append(self.execute_task(task, **kwargs))
      File "/home/runner/work/pybuilder/pybuilder/target/dist/pybuilder-0.13.0.dev/pybuilder/execution.py", line 337, in execute_task
        if self.execute_action(action, kwargs):
      File "/home/runner/work/pybuilder/pybuilder/target/dist/pybuilder-0.13.0.dev/pybuilder/execution.py", line 382, in execute_action
        action.execute(arguments)
      File "/home/runner/work/pybuilder/pybuilder/target/dist/pybuilder-0.13.0.dev/pybuilder/execution.py", line 95, in execute
        self.callable(*arguments)
      File "/home/runner/work/pybuilder/pybuilder/target/dist/pybuilder-0.13.0.dev/pybuilder/plugins/python/distutils_plugin.py", line 281, in build_binary_distribution
        execute_distutils(project, logger, reactor.pybuilder_venv, commands, True)
      File "/home/runner/work/pybuilder/pybuilder/target/dist/pybuilder-0.13.0.dev/pybuilder/plugins/python/distutils_plugin.py", line 396, in execute_distutils
        command, out_file, tail_log(out_file))
    pybuilder.errors.BuildFailedException: Error while executing setup command ['sdist']. See /tmp/IntegrationTestSupport6wqp1uy_/target/reports/distutils/sdist for full details:
    	running clean
    	'build/lib' does not exist -- can't clean it
    	'build/bdist.linux-x86_64' does not exist -- can't clean it
    	'build/scripts-3.6' does not exist -- can't clean it
    	running sdist
    	running egg_info
    	error: Invalid distribution name or version syntax: IntegrationTestSupport6wqp1uy--1.0.dev0