Steup Error

[xrivendell7]

When I use ROPGadget to find "pop|ret" in target programm "level4" ,i meet this error and i don't know how to fix it

!bash
ROPgadget --binary level4 --only "pop|ret" 
Traceback (most recent call last):
  File "/usr/local/bin/ROPgadget", line 4, in <module>
    __import__('pkg_resources').run_script('ROPGadget==5.4', 'ROPgadget')
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 738, in run_script
    self.require(requires)[0].run_script(script_name, ns)
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 1491, in run_script
    raise ResolutionError("No script named %r" % script_name)
pkg_resources.ResolutionError: No script named 'ROPgadget'

.I successfully install ROPGadget ,i have no idea about where is the problem...

!bash
pip install ROPGadget
The directory '/home/xingxing/.cache/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
The directory '/home/xingxing/.cache/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
Requirement already satisfied: ROPGadget in /home/xingxing/.local/lib/python2.7/site-packages
Requirement already satisfied: capstone in /home/xingxing/.local/lib/python2.7/site-packages (from ROPGadget)