我收到错误。我应该怎么解决？
错误：runTest（30_openram_test.openram_test）
c2有关信息，我正在Traceback (most recent call last): File "/home/leepil/OpenRAM-master/compiler/tests/30_openram_test.py", line 23, in runTest
globals.init_openram("config_20_{0}".format(OPTS.tech_name))
enter code here
File "/home/leepil/OpenRAM-master/compiler/tests/../globals.py", line 113, in init_openram
import_tech()
File "/home/leepil/OpenRAM-master/compiler/tests/../globals.py", line 314, in import_tech
__import__(filename)
File "/home/leepil/OpenRAM-master/technology/setup_scripts/setup_openram_freepdk45.py", line 16, in <module>
PDK_DIR=os.path.abspath(os.environ.get("FREEPDK45"))
File "/home/leepil/PycellStudio3/plat_linux_gcc44x_64/3rd/lib/python2.7/posixpath.py", line 367, in abspath
if not isabs(path):
File "/home/leepil/PycellStudio3/plat_linux_gcc44x_64/3rd/lib/python2.7/posixpath.py", line 61, in isabs
return s.startswith('/')
AttributeError: 'NoneType' object has no attribute 'startswith'
（技术是OpenRAM-Master）＆amp; Python版本2.7.9。
请参阅下面的详细错误消息。 THX！