Error with the example command `aenet sconv vasprun.xml final_structure.xsf`

[JQmasters]

Error message was:

Traceback (most recent call last):
  File "/Users/jianzhou/.local/bin/aenet", line 30, in <module>
    args.run(args)
  File "/Users/jianzhou/.local/lib/python3.9/site-packages/aenet/commandline/aenet_sconv.py", line 231, in run
    self.sconvert(infile=args.input_file,
  File "/Users/jianzhou/.local/lib/python3.9/site-packages/aenet/commandline/aenet_sconv.py", line 465, in sconvert
    struc = self. read_input_structure(
  File "/Users/jianzhou/.local/lib/python3.9/site-packages/aenet/commandline/aenet_sconv.py", line 290, in read_input_structure
    struc = structure.read_safely(infile, frmt=infrmt, **kwargs)
  File "/Users/jianzhou/.local/lib/python3.9/site-packages/aenet/io/structure.py", line 87, in read_safely
    struc = read(filename, frmt=frmt, **kwargs)
  File "/Users/jianzhou/.local/lib/python3.9/site-packages/aenet/io/structure.py", line 78, in read
    return formats[frmt].read(filename, **kwargs)
  File "/Users/jianzhou/.local/lib/python3.9/site-packages/aenet/formats/vasp.py", line 214, in read
    if has_lxml:
NameError: name 'has_lxml' is not defined

I tried to debug it:

In the ../aenet/formats/vasp.py file, line 11

try:
       from lxml import etree
       has_lxml = True
except ImportError:
       import xml.etree.cElementTree as ET

As I didn't install lxml package, the variable has_lxml is not defined. Thus on the line 214:

if has_lxml:
             parser = etree.XMLParser(recover=True, huge_tree=True)
             tree = etree.parse(infile, parser)

It reported one error.