def custom_importer(name, globals=None, locals=None, fromlist=None, level=-1):

    globals = globals or {}
    locals = locals or {}
    fromlist = fromlist or []

    try:
        if current.request._custom_import_track_changes:
            base_importer = TRACK_IMPORTER
        else:
            base_importer = NATIVE_IMPORTER
    except:  # there is no current.request (should never happen)
        base_importer = NATIVE_IMPORTER

    # if not relative and not from applications:
    if hasattr(current, 'request') \
            and level <= 0 \
            and not name.partition('.')[0] in INVALID_MODULES \
            and isinstance(globals, dict):
        import_tb = None
        try:
            try:
                oname = name if not name.startswith('.') else '.'+name
                return NATIVE_IMPORTER(oname, globals, locals, fromlist, level)
            except ImportError:
                items = current.request.folder.split(os.path.sep)
                if not items[-1]:
                    items = items[:-1]
                modules_prefix = '.'.join(items[-2:]) + '.modules'
                if not fromlist:
                    # import like "import x" or "import x.y"
                    result = None
                    for itemname in name.split("."):
                        new_mod = base_importer(
                            modules_prefix, globals, locals, [itemname], level)
                        try:
                            result = result or new_mod.__dict__[itemname]
                        except KeyError, e:
                            raise ImportError, 'Cannot import module %s' % str(e)
                        modules_prefix += "." + itemname
                    return result
                else:
                    # import like "from x import a, b, ..."
                    pname = modules_prefix + "." + name
                    return base_importer(pname, globals, locals, fromlist, level)
        except ImportError, e1:
            import_tb = sys.exc_info()[2]
            try:
                return NATIVE_IMPORTER(name, globals, locals, fromlist, level)
            except ImportError, e3:
                raise ImportError, e1, import_tb  # there an import error in the module
        except Exception, e2:
            raise e2  # there is an error in the module
        finally:
            if import_tb:
                import_tb = None

    return NATIVE_IMPORTER(name, globals, locals, fromlist, level)
Test mtime update in imports with no mtime given
dataset/ETHPy150Open uwdata/termite-visualizations/web2py/gluon/custom_import.py/custom_importer--crossover with--dataset/ETHPy150Open sahana/eden/modules/unit_tests/s3/s3resource.py/ResourceImportTests.testImportXMLWithoutMTime