Fix for Python 4

[hugovk]

Python 4 is some way off, but it may be a good idea to clean some of these up, similar to #2076.

---

This comparison is True for Python 3.3 - 3.99, but is False for Python 4 and would run the Python 2 - 3.2 code:

if sys.version_info.major == 3 and sys.version_info.minor >= 3:	
    from unittest.mock import patch
else:
    from mock import patch	

Because Python 3.3 is the minimum Python 3.x supported, it can be simplified:

-if sys.version_info.major == 3 and sys.version_info.minor >= 3:	
+if sys.version_info.major >= 3:	

---

Another couple of cases which fail on Python 4.0, here we need to compare the version_info tuple and avoid comparing the sys.version_info.minor integer:

-if sys.version_info.major == 3 and sys.version_info.minor >= 4:
+if sys.version_info >= (3, 4):

-if sys.version_info.major != 3 or sys.version_info.minor < 6:
+if sys.version_info < (3, 6):

---

Finally, there's some code which uses six.PY3, a bit like:

if six.PY3:
    print("Python 3+ code")
else:
    print "Python 2 code"

Where in six.py:

PY3 = sys.version_info[0] == 3

When run on Python 4, this will run the Python 2 code!

Instead, use six.PY2.

---

Found with https://github.com/asottile/flake8-2020.

[nicolaskruchten]

Thanks for this! I don't understand the following reasoning though:

Because Python 3.3 is the minimum Python 3.x supported, it can be simplified:

-if sys.version_info.major == 3 and sys.version_info.minor >= 3:
+if sys.version_info.major >= 3:

wouldn't this be a change in behaviour for 3.2?

[hugovk]

Yes, it would be a change in behaviour for 3.2.

Does plotly.py still support 3.2?

The classifiers at https://pypi.org/project/plotly/ suggest 2.7 and 3.3 - 3.7.

[nicolaskruchten]

No, but I'd rather these changes be pure refactorings that don't change behaviour if possible, to avoid unintended side-effects :)

[hugovk]

Sure thing, will update tomorrow!

[nicolaskruchten]

Thanks very much for bringing this up and fixing it for us :)

[hugovk]

You're welcome, and updated:

-if sys.version_info.major == 3 and sys.version_info.minor >= 3:
+if sys.version_info >= (3, 3):

[nicolaskruchten]

LGTM... @jonmmease @emmanuelle thoughts?

[hugovk]

As suggested in #2076 (comment), I've combined PR #2076 with this one.

[nicolaskruchten]

OK nice so this basically mostly impacts tests, and all the tests are passing! We'll merge this in before the 4.5 release next week unless anyone brings up any objections by then. Thanks again!

[emmanuelle]

Thank you very much!

[hugovk]

You're welcome!