def subst_vars(s, local_vars):
    """
    Perform variable substitution on 'string'.
    Variables are indicated by format-style braces ("{var}").
    Variable is substituted by the value found in the 'local_vars'
    dictionary or in 'os.environ' if it's not in 'local_vars'.
    'os.environ' is first checked/augmented to guarantee that it contains
    certain values: see 'check_environ()'.  Raise ValueError for any
    variables not found in either 'local_vars' or 'os.environ'.
    """
    check_environ()
    lookup = dict(os.environ)
    lookup.update((name, str(value)) for name, value in local_vars.items())
    try:
        return _subst_compat(s).format_map(lookup)
    except KeyError as var:
        raise ValueError(f"invalid variable {var}")

    Perform variable substitution on 'string'.
    Variables are indicated by format-style braces ("{var}").
    Variable is substituted by the value found in the 'local_vars'
    dictionary or in 'os.environ' if it's not in 'local_vars'.
    'os.environ' is first checked/augmented to guarantee that it contains
    certain values: see 'check_environ()'.  Raise ValueError for any
    variables not found in either 'local_vars' or 'os.environ'.
    
product/gradle-plugin/src/main/python/setuptools/_distutils/util.py