def check_string_in_file(in_file, string):
    """
    Check whether a string is found inside a text file.
    Return True if found, else False.

    >>> in_file = "test_data/test_run.log"
    >>> check_string_in_file(in_file, "AssertionError")
    True
    >>> in_file = "test_data/empty_file"
    >>> check_string_in_file(in_file, "AssertionError")
    False

    """

    found = False

    f = open(in_file, "r")
    for line in f:
        if string in line:
            found = True
            break
    f.close()

    return found