Heisenbug when launching tests

Hello all,

I have a random bug when I launch check-all:

lit.py: discovery.py:224: warning: input ‘/home/black/llvm/build/projects/compiler-rt/test/asan/Unit’ contained no tests
lit.py: discovery.py:224: warning: input ‘/home/black/llvm/build/projects/compiler-rt/test/sanitizer_common’ contained no tests
lit.py: discovery.py:190: warning: test suite ‘ThreadSanitizer-Unit’ contained no tests
lit.py: lit.cfg:196: note: using clang: ‘/home/black/llvm/build/./bin/clang’
lit.py: TestingConfig.py:108: fatal: unable to parse config file ‘/home/black/llvm/src/tools/clang/test/lit.cfg’, traceback: Traceback (most recent call last):
File “/usr/home/black/llvm/src/utils/lit/lit/TestingConfig.py”, line 95, in load_from_path
exec(compile(data, path, ‘exec’), cfg_globals, None)
File “/home/black/llvm/src/tools/clang/test/lit.cfg”, line 258, in
getClangBuiltinIncludeDir(config.clang))) )
File “/home/black/llvm/src/tools/clang/test/lit.cfg”, line 221, in getClangBuiltinIncludeDir
stdout=subprocess.PIPE)
File “/usr/local/lib/python2.7/subprocess.py”, line 709, in init
errread, errwrite)
File “/usr/local/lib/python2.7/subprocess.py”, line 1326, in _execute_child
raise child_exception
OSError: [Errno 13] Permission denied

It occurs sometimes, “randomly”, even if I don’t touch any file.
Do you know what is the root of this problem? How can I solve it definitively?

Thanks by advance for your help.