fix output handling of subproc_call

.github/ISSUE_TEMPLATE/unexpected-problems---bugs.md

@@ -26,6 +26,9 @@ feel free to delete everything in this template.
 ### 2. What you observed:
 
 (1) **Include the ENTIRE logs here:**
+```
+<paste logs here>
+```
 
 It's always better to copy-paste what you observed instead of describing them.
 
@@ -44,15 +47,11 @@ If you expect higher speed, please read
 http://tensorpack.readthedocs.io/tutorial/performance-tuning.html
 before posting.
 
-If you expect the model to work better, only in one of the two conditions can we help with it:
+If you expect the model to converge / work better, note that we do not help you on how to train a new model.
+Only in one of the two conditions can we help with it:
 (1) You're unable to reproduce the results documented in tensorpack examples.
 (2) It appears to be a tensorpack bug.
 
-Otherwise, how to train a good model on your task or your
-modifications is a machine learning question.
-We do not answer machine learning questions and it is your responsibility to
-figure out how to make your models more accurate.
-
 ### 4. Your environment:
 
 Paste the output of this command: `python -c 'import tensorpack.tfutils as u; print(u.collect_env_info())'`

tensorpack/utils/concurrency.py

@@ -257,8 +257,11 @@ def subproc_call(cmd, timeout=None):
         return output, 0
     except subprocess.TimeoutExpired as e:
         logger.warn("Command '{}' timeout!".format(cmd))
-        logger.warn(e.output.decode('utf-8'))
-        return e.output, -1
+        if e.output:
+            logger.warn(e.output.decode('utf-8'))
+            return e.output, -1
+        else:
+            return "", -1
     except subprocess.CalledProcessError as e:
         logger.warn("Command '{}' failed, return code={}".format(cmd, e.returncode))
         logger.warn(e.output.decode('utf-8'))