capybara/virtualenv/lib/python2.7/site-packages/pip/req/req_install.py
def from_line(
            cls, name, comes_from=None, isolated=False, options=None,
            wheel_cache=None):
        """Creates an InstallRequirement from a name, which might be a
        requirement, directory containing 'setup.py', filename, or URL.
        """
        from pip.index import Link

        if is_url(name):
            marker_sep = '; '
        else:
            marker_sep = ';'
        if marker_sep in name:
            name, markers = name.split(marker_sep, 1)
            markers = markers.strip()
            if not markers:
                markers = None
        else:
            markers = None
        name = name.strip()
        req = None
        path = os.path.normpath(os.path.abspath(name))
        link = None
        extras = None

        if is_url(name):
            link = Link(name)
        else:
            p, extras = _strip_extras(path)
            if (os.path.isdir(p) and
                    (os.path.sep in name or name.startswith('.'))):

                if not is_installable_dir(p):
                    raise InstallationError(
                        "Directory %r is not installable. File 'setup.py' "
                        "not found." % name
                    )
                link = Link(path_to_url(p))
            elif is_archive_file(p):
                if not os.path.isfile(p):
                    logger.warning(
                        'Requirement %r looks like a filename, but the '
                        'file does not exist',
                        name
                    )
                link = Link(path_to_url(p))

        # it's a local file, dir, or url
        if link:
            # Handle relative file URLs
            if link.scheme == 'file' and re.search(r'\.\./', link.url):
                link = Link(
                    path_to_url(os.path.normpath(os.path.abspath(link.path))))
            # wheel file
            if link.is_wheel:
                wheel = Wheel(link.filename)  # can raise InvalidWheelFilename
                if not wheel.supported():
                    raise UnsupportedWheel(
                        "%s is not a supported wheel on this platform." %
                        wheel.filename
                    )
                req = "%s==%s" % (wheel.name, wheel.version)
            else:
                # set the req to the egg fragment.  when it's not there, this
                # will become an 'unnamed' requirement
                req = link.egg_fragment

        # a requirement specifier
        else:
            req = name

        options = options if options else {}
        res = cls(req, comes_from, link=link, markers=markers,
                  isolated=isolated, options=options,
                  wheel_cache=wheel_cache)

        if extras:
            res.extras = pkg_resources.Requirement.parse('__placeholder__' +
                                                         extras).extras

        return res
def from_line(
            cls, name, comes_from=None, isolated=False, options=None,
            wheel_cache=None):
        """Creates an InstallRequirement from a name, which might be a
        requirement, directory containing 'setup.py', filename, or URL.
        """
        from pip.index import Link

        if is_url(name):
            marker_sep = '; '
        else:
            marker_sep = ';'
        if marker_sep in name:
            name, markers = name.split(marker_sep, 1)
            markers = markers.strip()
            if not markers:
                markers = None
        else:
            markers = None
        name = name.strip()
        req = None
        path = os.path.normpath(os.path.abspath(name))
        link = None
        extras = None

        if is_url(name):
            link = Link(name)
        else:
            p, extras = _strip_extras(path)
            if (os.path.isdir(p) and
                    (os.path.sep in name or name.startswith('.'))):

                if not is_installable_dir(p):
                    raise InstallationError(
                        "Directory %r is not installable. File 'setup.py' "
                        "not found." % name
                    )
                link = Link(path_to_url(p))
            elif is_archive_file(p):
                if not os.path.isfile(p):
                    logger.warning(
                        'Requirement %r looks like a filename, but the '
                        'file does not exist',
                        name
                    )
                link = Link(path_to_url(p))

        # it's a local file, dir, or url
        if link:
            # Handle relative file URLs
            if link.scheme == 'file' and re.search(r'\.\./', link.url):
                link = Link(
                    path_to_url(os.path.normpath(os.path.abspath(link.path))))
            # wheel file
            if link.is_wheel:
                wheel = Wheel(link.filename)  # can raise InvalidWheelFilename
                if not wheel.supported():
                    raise UnsupportedWheel(
                        "%s is not a supported wheel on this platform." %
                        wheel.filename
                    )
                req = "%s==%s" % (wheel.name, wheel.version)
            else:
                # set the req to the egg fragment.  when it's not there, this
                # will become an 'unnamed' requirement
                req = link.egg_fragment

        # a requirement specifier
        else:
            req = name

        options = options if options else {}
        res = cls(req, comes_from, link=link, markers=markers,
                  isolated=isolated, options=options,
                  wheel_cache=wheel_cache)

        if extras:
            res.extras = pkg_resources.Requirement.parse('__placeholder__' +
                                                         extras).extras

        return res
Creates an InstallRequirement from a name, which might be a
        requirement, directory containing 'setup.py', filename, or URL.