How to use the bypy.constants.SRC function in bypy

def build_c_extensions(ext_dir, args):
    bdir = os.path.join(build_dir(), 'calibre-extension-objects')
    cmd = [
        PYTHON, 'setup.py', 'build',
        '--output-dir', ext_dir, '--build-dir', bdir,
    ]
    if args.build_only:
        cmd.extend(('--only', args.build_only))
    if run(*cmd, COMPILER_CWD=bdir) != 0:
        print('Building of calibre C extensions failed', file=sys.stderr)
        os.chdir(CALIBRE_DIR)
        run_shell()
        raise SystemExit('Building of calibre C extensions failed')
    return ext_dir

for pat in ('PyQt5\\uic\\port_v3', ):
        x = glob.glob(j(env.lib_dir, 'site-packages', pat))[0]
        shutil.rmtree(x)
    pyqt = j(env.lib_dir, 'site-packages', 'PyQt5')
    for x in {x for x in os.listdir(pyqt) if x.endswith('.pyd')}:
        if x.partition('.')[0] not in PYQT_MODULES and x != 'sip.pyd':
            os.remove(j(pyqt, x))
    with open(j(pyqt, '__init__.py') , 'r+b') as f:
        raw = f.read()
        nraw = raw.replace(b'def find_qt():', b'def find_qt():\n    return # disabled for calibre')
        if nraw == raw:
            raise Exception('Failed to patch PyQt to disable dll directory manipulation')
        f.seek(0), f.truncate(), f.write(nraw)

    printf('Adding calibre sources...')
    for x in glob.glob(j(CALIBRE_DIR, 'src', '*')):
        if os.path.isdir(x):
            if os.path.exists(os.path.join(x, '__init__.py')):
                shutil.copytree(x, j(sp_dir, b(x)), ignore=shutil.ignore_patterns('*.pyc', '*.pyo'))
        else:
            shutil.copy(x, j(sp_dir, b(x)))

    for x in (r'calibre\manual', r'calibre\plugins', 'pythonwin'):
        deld = j(sp_dir, x)
        if os.path.exists(deld):
            shutil.rmtree(deld)

    for x in os.walk(j(sp_dir, 'calibre')):
        for f in x[-1]:
            if not f.endswith('.py'):
                os.remove(j(x[0], f))

def add_site_packages(self):
        print('\nAdding site-packages')
        os.makedirs(self.site_packages)
        sys_path = json.loads(subprocess.check_output([
            PYTHON, '-c', 'import sys, json; json.dump(sys.path, sys.stdout)']))
        paths = reversed(tuple(map(abspath, [x for x in sys_path if x.startswith('/') and not x.startswith('/Library/')])))
        upaths = []
        for x in paths:
            if x not in upaths and (x.endswith('.egg') or x.endswith('/site-packages')):
                upaths.append(x)
        upaths.append(join(CALIBRE_DIR, 'src'))
        for x in upaths:
            print('\t', x)
            tdir = None
            try:
                if not os.path.isdir(x):
                    zf = zipfile.ZipFile(x)
                    tdir = tempfile.mkdtemp()
                    zf.extractall(tdir)
                    x = tdir
                self.add_modules_from_dir(x)
                self.add_packages_from_dir(x)
            finally:
                if tdir is not None:
                    shutil.rmtree(tdir)
        try:
            shutil.rmtree(join(self.site_packages, 'calibre', 'plugins'))

def run(*args, **extra_env):
    env = os.environ.copy()
    env.update(worker_env)
    env.update(extra_env)
    env['SW'] = PREFIX
    env['LD_LIBRARY_PATH'] = LIBDIR
    env['SIP_BIN'] = os.path.join(PREFIX, 'bin', 'sip')
    env['QMAKE'] = os.path.join(PREFIX, 'qt', 'bin', 'qmake')
    return subprocess.call(list(args), env=env, cwd=CALIBRE_DIR)

def __init__(self):
        self.src_root = CALIBRE_DIR
        self.base = mkdtemp('frozen-')
        self.lib_dir = j(self.base, 'lib')
        self.py_dir = j(self.lib_dir, 'python' + py_ver)
        os.makedirs(self.py_dir)
        self.bin_dir = j(self.base, 'bin')
        os.mkdir(self.bin_dir)
        self.SRC = j(self.src_root, 'src')
        self.obj_dir = mkdtemp('launchers-')

def read_cal_file(name):
    with open(os.path.join(CALIBRE_DIR, 'src', 'calibre', name), 'rb') as f:
        return f.read().decode('utf-8')

for pat in ('PyQt5\\uic\\port_v3', ):
        x = glob.glob(j(env.lib_dir, 'site-packages', pat))[0]
        shutil.rmtree(x)
    pyqt = j(env.lib_dir, 'site-packages', 'PyQt5')
    for x in {x for x in os.listdir(pyqt) if x.endswith('.pyd')}:
        if x.partition('.')[0] not in PYQT_MODULES and x != 'sip.pyd':
            os.remove(j(pyqt, x))
    with open(j(pyqt, '__init__.py') , 'r+b') as f:
        raw = f.read()
        nraw = raw.replace(b'def find_qt():', b'def find_qt():\n    return # disabled for calibre')
        if nraw == raw:
            raise Exception('Failed to patch PyQt to disable dll directory manipulation')
        f.seek(0), f.truncate(), f.write(nraw)

    printf('Adding calibre sources...')
    for x in glob.glob(j(CALIBRE_DIR, 'src', '*')):
        if os.path.isdir(x):
            if os.path.exists(os.path.join(x, '__init__.py')):
                shutil.copytree(x, j(sp_dir, b(x)), ignore=shutil.ignore_patterns('*.pyc', '*.pyo'))
        else:
            shutil.copy(x, j(sp_dir, b(x)))

    for x in (r'calibre\manual', r'calibre\plugins', 'pythonwin'):
        deld = j(sp_dir, x)
        if os.path.exists(deld):
            shutil.rmtree(deld)

    for x in os.walk(j(sp_dir, 'calibre')):
        for f in x[-1]:
            if not f.endswith('.py'):
                os.remove(j(x[0], f))