我使用linux mint并以管理员身份登录。我之前使用过pip来安装软件包，但是现在无论我尝试安装什么，我都会收到此错误
Exception:
Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/basecommand.py", line 122, in main
status = self.run(options, args)
File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/commands/install.py", line 283, in run
requirement_set.install(install_options, global_options, root=options.root_path)
File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/req.py", line 1435, in install
requirement.install(install_options, global_options, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/req.py", line 671, in install
self.move_wheel_files(self.source_dir, root=root)
File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/req.py", line 901, in move_wheel_files
pycompile=self.pycompile,
File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/wheel.py", line 215, in move_wheel_files
clobber(source, lib_dir, True)
File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/wheel.py", line 205, in clobber
os.makedirs(destdir)
File "/usr/lib/python2.7/os.py", line 157, in makedirs
mkdir(name, mode)
OSError: [Errno 13] Permission denied: '/usr/local/lib/python2.7/dist-packages/IPython'
Storing debug log for failure in /home/t90/.pip/pip.log
可能是什么问题？