EasyClangComplete: subprocess call throws OSError: [WinError 6] The handle is invalid on Windows

Solved, this fixed it:

utils.py

@staticmethod
def find_libclang_dir(clang_binary):
    """ Find directory with libclang

    Args:
        clang_binary (str): clang binary to call

    Returns:
        str: folder with libclang
    """
    stdin = None
    stderr = None
    log.debug(" platform: %s", platform.architecture())
    log.debug(" python version: %s", platform.python_version())
    for suffix in ClangUtils.get_suffixes():
        # pick a name for a file
        log.info(" we are on '%s'", platform.system())
        file = "libclang{}".format(suffix)
        log.info(" searching for: '%s'", file)
        startupinfo = None
        # let's find the library
        if platform.system() == "Darwin":
            # [HACK]: wtf??? why does it not find libclang.dylib?
            get_library_path_cmd = [clang_binary, "-print-file-name="]
        elif platform.system() == "Windows":
            get_library_path_cmd = [clang_binary, "-print-prog-name="]
            # Don't let console window pop-up briefly.
            startupinfo = subprocess.STARTUPINFO()
            startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
            startupinfo.wShowWindow = subprocess.SW_HIDE
            stdin = subprocess.PIPE
            stderr = subprocess.PIPE
        else:
            get_library_path_cmd = [clang_binary, "-print-file-name={}".format(file)]
        output = subprocess.check_output(
            get_library_path_cmd,
            stdin=stdin,
            stderr=stderr,
            startupinfo=startupinfo).decode('utf8').strip()
        log.info(" libclang search output = '%s'", output)
        if output:
            libclang_dir = ClangUtils.dir_from_output(output)
            if path.isdir(libclang_dir) and path.exists(path.join(libclang_dir, file)):
                log.info(" found libclang dir: '%s'", libclang_dir)
                log.info(" found library file: '%s'", file)
                ClangUtils.libclang_name = file
                return libclang_dir
        log.warning(" clang could not find '%s'", file)
    # if we haven't found anything there is nothing to return
    log.error(" no libclang found at all")
    return None

tools.py

@staticmethod
def run_command(command, shell=True):
    """ Run a generic command in a subprocess

    Args:
        command (str): command to run

    Returns:
        str: raw command output
    """
    try:
        stdin = None
        startupinfo = None
        if isinstance(command, list):
            command = subprocess.list2cmdline(command)
            log.debug(" command: \n%s", command)
        if platform.system() == "Windows":
            # Don't let console window pop-up briefly.
            startupinfo = subprocess.STARTUPINFO()
            startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
            startupinfo.wShowWindow = subprocess.SW_HIDE
            stdin = subprocess.PIPE
        output = subprocess.check_output(command,
                                         stdin=stdin,
                                         stderr=subprocess.STDOUT,
                                         shell=shell,
                                         startupinfo=startupinfo)
        output_text = ''.join(map(chr, output))
    except subprocess.CalledProcessError as e:
        output_text = e.output.decode("utf-8")
        log.debug(" clang process finished with code: %s", e.returncode)
        log.debug(" clang process output: \n%s", output_text)
    return output_text

Credits for this workaround/fix goes for @wbond