PEP8: Avoid bare except:

[cclauss]

Do not use bare except:, it also catches unexpected events like memory errors, interrupts, system exit, and so on.
Prefer except Exception:. If you’re sure what you’re doing, be explicit and write except BaseException:.

https://realpython.com/the-most-diabolical-python-antipattern/
https://www.python.org/dev/peps/pep-0008/

$ python3 -c "basestring" # --> NameError: name 'basestring' is not defined

$ BUILTINS=assert_equals,assert_exception,inputs,is_resumed,NUM_FOREACH,NUM_LINES,ResumeFromHere,TestRetry
$ flake8 . --builtins=$BUILTINS --count --select=E9,F63,F7,F82 --show-source --statistics

./metaflow/metaflow/parameters.py:13:15: F821 undefined name 'basestring'
    strtype = basestring
              ^
./metaflow/metaflow/util.py:16:20: F821 undefined name 'unicode'
    unicode_type = unicode
                   ^