Runtime error with output report

Running into this error when executing:

DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
REPO_DIR="`realpath $DIR/../mypackage`"
EXCLUDES=$REPO_DIR/version.py
bandit "$REPO_DIR" -ll -r -x "$EXCLUDES"```

Output is

[main]  INFO    profile include tests: None
[main]  INFO    profile exclude tests: None
[main]  INFO    cli include tests: None
[main]  INFO    cli exclude tests: None
[main]  INFO    running on Python 3.7.3
Traceback (most recent call last):
  File "c:\users\pimentelc\appdata\local\continuum\anaconda3\envs\venv-datasci\lib\site-packages\bandit\core\manager.py", line 169, in output_results
    conf_level=conf_level, lines=lines)
  File "c:\users\pimentelc\appdata\local\continuum\anaconda3\envs\venv-datasci\lib\site-packages\bandit\formatters\text.py", line 167, in report
    with fileobj:
AttributeError: __enter__

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "c:\users\pimentelc\appdata\local\continuum\anaconda3\envs\venv-datasci\lib\runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "c:\users\pimentelc\appdata\local\continuum\anaconda3\envs\venv-datasci\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "C:\Users\pimentelc\AppData\Local\Continuum\anaconda3\envs\venv-datasci\Scripts\bandit.exe\__main__.py", line 9, in <module>
  File "c:\users\pimentelc\appdata\local\continuum\anaconda3\envs\venv-datasci\lib\site-packages\bandit\cli\main.py", line 403, in main
    args.msg_template)
  File "c:\users\pimentelc\appdata\local\continuum\anaconda3\envs\venv-datasci\lib\site-packages\bandit\core\manager.py", line 173, in output_results
    "%s" % (output_format, str(e)))
RuntimeError: Unable to output report using 'txt' formatter: __enter__

Bandit version
bandit 1.6.0, Anaconda python 3.7

Reproduce the command with Bandit 1.6.0 and Python 3.7, then start in bandit/core/manager.py around output_results and bandit/formatters/text.py around report. Confirm the failure path for the txt formatter and ensure the report completes without the enter error.