handle error in find_library

examples/DeepQNetwork/README.md

@@ -18,7 +18,7 @@ used a modified version where each batch contains transitions from different sim
 ## Usage:
 
 ### With ALE (paper's setting):
-Install [ALE](https://github.com/mgbellemare/Arcade-Learning-Environment) and gym.
+Install [ALE](https://github.com/mgbellemare/Arcade-Learning-Environment) and `gym[atari]`.
 
 Download an [atari rom](https://github.com/openai/atari-py/tree/gdb/atari_py/atari_roms), e.g.:
 ```

tensorpack/utils/utils.py

@@ -251,15 +251,20 @@ def find_library_full_path(name):
         procmap = os.path.join('/proc', str(os.getpid()), 'maps')
         if not os.path.isfile(procmap):
             return None
-        with open(procmap, 'r') as f:
-            for line in f:
-                line = line.strip().split(' ')
-                sofile = line[-1]
-
-                basename = os.path.basename(sofile)
-                if 'lib' + name + '.so' in basename:
-                    if os.path.isfile(sofile):
-                        return os.path.realpath(sofile)
+        try:
+            with open(procmap, 'r') as f:
+                for line in f:
+                    line = line.strip().split(' ')
+                    sofile = line[-1]
+
+                    basename = os.path.basename(sofile)
+                    if 'lib' + name + '.so' in basename:
+                        if os.path.isfile(sofile):
+                            return os.path.realpath(sofile)
+        except PermissionError:
+            # can fail in certain environment (e.g. chroot)
+            # if the pids are incorrectly mapped
+            pass
 
     # The following two methods come from https://github.com/python/cpython/blob/master/Lib/ctypes/util.py
     def _use_ld(name):