pep8

just a quick PR to fix all the errors reported by flake8

BTW, I saw that quite a few multi line strings are written in the following manner:

```python
def foo(bar):
    some_text = some_func("""some line
some continuing line
""")
    some_other = code_here
```

Did you know that this is equivalent to the following code?

```python
def foo(bar):
    some_text = some_func("""some line"""
                          """some continuing line""")
    some_other = code_here
```

It's a matter of test I guess, I usually prefer having the whitespace/indentation preserved in the code, and writing the multi line strings like that duplicates the quotes (beginning and end of each line), but keeps the overall "indented" look of the code.

What do you think, would you like me to change it everywhere I see it, or leave it like that?