Test failures with pyparsing 3.2.1

[FliegendeWurst]

Testing asn1tools 0.167.0 with pyparsing 3.2.1 yields several test failures: (full log)

=========================== short test summary info ============================
FAILED tests/test_compile.py::Asn1ToolsCompileTest::test_missing_parameterized_value - IndexError: string index out of range
FAILED tests/test_command_line.py::Asn1ToolsCommandLineTest::test_command_line_generate_c_source_oer - IndexError: string index out of range
FAILED tests/test_parse.py::Asn1ToolsParseTest::test_parse_parameterization - IndexError: string index out of range
FAILED tests/test_codecs_consistency.py::Asn1ToolsCodecsConsistencyTest::test_c_source - IndexError: string index out of range
FAILED tests/test_oer.py::Asn1ToolsOerTest::test_c_source - IndexError: string index out of range
FAILED tests/test_command_line.py::Asn1ToolsCommandLineTest::test_command_line_generate_c_source_uper - SystemExit: error: string index out of range
FAILED tests/test_command_line.py::Asn1ToolsCommandLineTest::test_command_line_generate_rust_source_uper - SystemExit: error: string index out of range
======================== 7 failed, 465 passed in 7.78s =========================

Most likely due to pyparsing/pyparsing#573.