If "uname -rs" returns no output, _parse_uname_content causes exception

Python version 3.5.2 OS: Ubuntu 16.04.6 LTS

I’m trying to install pip by using python3 get-pip.py --user. This is failing with “IndexError: list index out of range”. Running a debugger shows that the root cause seems to be that uname -rs returns no output on my system. The individual options work but not when combined.

Here is the exception stack trace:

Exception:
Traceback (most recent call last):
  File "/tmp/tmpyrz_zul1/pip.zip/pip/_internal/cli/base_command.py", line 143, in main
    status = self.run(options, args)
  File "/tmp/tmpyrz_zul1/pip.zip/pip/_internal/commands/install.py", line 259, in run
    with self._build_session(options) as session:
  File "/tmp/tmpyrz_zul1/pip.zip/pip/_internal/cli/base_command.py", line 79, in _build_session
    insecure_hosts=options.trusted_hosts,
  File "/tmp/tmpyrz_zul1/pip.zip/pip/_internal/download.py", line 337, in __init__
    self.headers["User-Agent"] = user_agent()
  File "/tmp/tmpyrz_zul1/pip.zip/pip/_internal/download.py", line 100, in user_agent
    zip(["name", "version", "id"], distro.linux_distribution()),
  File "/tmp/tmpyrz_zul1/pip.zip/pip/_vendor/distro.py", line 120, in linux_distribution
    return _distro.linux_distribution(full_distribution_name)
  File "/tmp/tmpyrz_zul1/pip.zip/pip/_vendor/distro.py", line 675, in linux_distribution
    self.version(),
  File "/tmp/tmpyrz_zul1/pip.zip/pip/_vendor/distro.py", line 741, in version
    self.uname_attr('release')
  File "/tmp/tmpyrz_zul1/pip.zip/pip/_vendor/distro.py", line 910, in uname_attr
    return self._uname_info.get(attribute, '')
  File "/tmp/tmpyrz_zul1/pip.zip/pip/_vendor/distro.py", line 550, in __get__
    ret = obj.__dict__[self._fname] = self._f(obj)
  File "/tmp/tmpyrz_zul1/pip.zip/pip/_vendor/distro.py", line 1037, in _uname_info
    return self._parse_uname_content(content)
  File "/tmp/tmpyrz_zul1/pip.zip/pip/_vendor/distro.py", line 1042, in _parse_uname_content
    match = re.search(r'^([^\s]+)\s+([\d\.]+)', lines[0].strip())
IndexError: list index out of range

[HorlogeSkynet]

@brejoc I guess content and len(content) >= 1 would be a nit pick ; checking for content boolean evaluation should be sufficient.

[HorlogeSkynet]

Closing here as #304 is almost there.