def pip(self, package_names, raise_on_error=True):
if isinstance(package_names, basestring):<EOL><INDENT>package_names = [package_names]<EOL><DEDENT>cmd = "<STR_LIT>" % ('<STR_LIT:U+0020>'.join(package_names))<EOL>return self.wait(cmd, raise_on_error=raise_on_error)<EOL>
Install specified python packages using pip. -U option added
Waits for command to finish.

Parameters
----------
package_names: list-like of str
raise_on_error: bool, default True
    If True then raise ValueError if stderr is not empty