Traverse a path ($PATH by default) to find the protoc compiler

def find_protoc(path=os.environ['PATH']):
    '''
    Traverse a path ($PATH by default) to find the protoc compiler
    '''
    protoc_filename = 'protoc'

    bin_search_paths = path.split(':') or []
    for search_path in bin_search_paths:
        bin_path = os.path.join(search_path, protoc_filename)
        if os.path.isfile(bin_path) and os.access(bin_path, os.X_OK):
            return bin_path

    raise ProtocNotFound("Protobuf compiler not found")