Bench run-tests causes "Exception: This statement can cause implicit commit"

Gentlemen,
I seem to have an issue with running tests. I have this simple test-class for DocType “Email Log” in erpituc/erpituc/erpituc/doctype/email_log/test_email_log.py:

class TestEmailLog(unittest.TestCase):
	
	def setUp(self) -> None:
		print("setUp called")
	
	def test_something(self):
		self.assertTrue("All is well")

But when i run

frappe@erpnextthkr:~/frappe-bench$ bench setup requirements --dev
frappe@erpnextthkr:~/frappe-bench$ bench --site erpnextthkr.schloss.ituc.de set-config allow_tests true
frappe@erpnextthkr:~/frappe-bench$ bench run-tests --doctype "Email Log" --skip-test-records --skip-before-tests

This exception happens:

frappe@erpnextthkr:~/frappe-bench$ bench run-tests --doctype "Email Log" --skip-test-records --skip-before-tests
Traceback (most recent call last):
  File "/usr/lib/python3.7/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib/python3.7/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/utils/bench_helper.py", line 104, in <module>
    main()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/utils/bench_helper.py", line 19, in main
    click.Group(commands=commands)(prog_name='bench')
  File "/home/frappe/frappe-bench/env/lib/python3.7/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "/home/frappe/frappe-bench/env/lib/python3.7/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/home/frappe/frappe-bench/env/lib/python3.7/site-packages/click/core.py", line 1259, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/frappe/frappe-bench/env/lib/python3.7/site-packages/click/core.py", line 1259, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/frappe/frappe-bench/env/lib/python3.7/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/frappe/frappe-bench/env/lib/python3.7/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/home/frappe/frappe-bench/env/lib/python3.7/site-packages/click/decorators.py", line 21, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/commands/__init__.py", line 27, in _func
    ret = f(frappe._dict(ctx.obj), *args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/commands/utils.py", line 588, in run_tests
    ui_tests=ui_tests, doctype_list_path=doctype_list_path, failfast=failfast)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/test_runner.py", line 70, in main
    ret = run_tests_for_doctype(doctype, verbose, tests, force, profile, failfast=failfast, junit_xml_output=junit_xml_output)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/test_runner.py", line 174, in run_tests_for_doctype
    return _run_unittest(modules, verbose=verbose, tests=tests, profile=profile, failfast=failfast, junit_xml_output=junit_xml_output)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/test_runner.py", line 186, in _run_unittest
    frappe.db.begin()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/database/database.py", line 769, in begin
    self.sql("START TRANSACTION")
  File "/home/frappe/frappe-bench/apps/frappe/frappe/database/database.py", line 124, in sql
    self.check_transaction_status(query)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/database/database.py", line 263, in check_transaction_status
    raise Exception('This statement can cause implicit commit')
Exception: This statement can cause implicit commit

So how to use “bench run-tests”?
I also searched the forum and found this (Tutorial: ERPNext Python Testing), but it didn’t help me with this particular error.