fix

python/petsclsys.py

@@ -28,7 +28,7 @@ import ctypes
 import os
 
 petscpath = os.environ["PETSC_DIR"]+"/"+os.environ["PETSC_ARCH"]+"/lib"
-os.environ["LD_LIBRARY_PATH"] += ":"+petscpath
+os.environ["LD_LIBRARY_PATH"] = os.environ.get("LD_LIBRARY_PATH","")+":"+petscpath
 try:
     lib = np.ctypeslib.load_library("libpetsc",petscpath)
 except: