capybara/virtualenv/lib/python2.7/site-packages/pip/_vendor/pkg_resources/__init__.py
def insert_on(self, path, loc = None):
        """Insert self.location in path before its nearest parent directory"""

        loc = loc or self.location
        if not loc:
            return

        nloc = _normalize_cached(loc)
        bdir = os.path.dirname(nloc)
        npath= [(p and _normalize_cached(p) or p) for p in path]

        for p, item in enumerate(npath):
            if item == nloc:
                break
            elif item == bdir and self.precedence == EGG_DIST:
                # if it's an .egg, give it precedence over its directory
                if path is sys.path:
                    self.check_version_conflict()
                path.insert(p, loc)
                npath.insert(p, nloc)
                break
        else:
            if path is sys.path:
                self.check_version_conflict()
            path.append(loc)
            return

        # p is the spot where we found or inserted loc; now remove duplicates
        while True:
            try:
                np = npath.index(nloc, p+1)
            except ValueError:
                break
            else:
                del npath[np], path[np]
                # ha!
                p = np

        return
def insert_on(self, path, loc = None):
        """Insert self.location in path before its nearest parent directory"""

        loc = loc or self.location
        if not loc:
            return

        nloc = _normalize_cached(loc)
        bdir = os.path.dirname(nloc)
        npath= [(p and _normalize_cached(p) or p) for p in path]

        for p, item in enumerate(npath):
            if item == nloc:
                break
            elif item == bdir and self.precedence == EGG_DIST:
                # if it's an .egg, give it precedence over its directory
                if path is sys.path:
                    self.check_version_conflict()
                path.insert(p, loc)
                npath.insert(p, nloc)
                break
        else:
            if path is sys.path:
                self.check_version_conflict()
            path.append(loc)
            return

        # p is the spot where we found or inserted loc; now remove duplicates
        while True:
            try:
                np = npath.index(nloc, p+1)
            except ValueError:
                break
            else:
                del npath[np], path[np]
                # ha!
                p = np

        return
Insert self.location in path before its nearest parent directory