Problems with doi2pdf on Mac OS

[kellertuer]

I am having trouble using doi2pdf on Mac OS. With the python version

> python --version
Python 3.6.6 :: Anaconda, Inc.

I had to change line 50 of doi2pdfnames.py to

print(filename.encode("utf8"))

to make it work with python3, but then I get

Traceback (most recent call last):
  File "~/Work/Software/mathbin/doi2pdfname.py", line 3, in <module>
    from lxml import etree
ModuleNotFoundError: No module named 'lxml'

even before it fetches the pdf; still it stops after storing the temporary file without renaming.

[rolandherzog]

lxml needs to be installed for Python3. For Ubuntu there is a package so sudo apt install python3-lxml installed it for me. However there are other issues; possibly due to a syntax change in the Python3 version of lxml.
@gerw: I think it would be beneficial to switch to Python3 in the near future.

[gerw]

I have translated doi2pdfname.py to Python 3.