adding solution for fatal error due to systemroot env variable missing

Author: kapilkd13

windowsdoc.md

@@ -118,7 +118,8 @@ on your local machine, you should be able to write to that folder inside Docker
 Container also (provided same user initiated Docker). In all it is a file
 permission issue.
 
-### Workflows with Javascript Expressions occasionally give Timeout errors  
+### Workflows with Javascript Expressions occasionally give Timeout errors
+
 To evaluate Javascript Expressions, cwltool looks for Nodejs on your system.
 In case Nodejs isn't installed, JS expressions are executed in a Docker Container.
 In order to avoid waiting forever in case error occurs, cwltool times out js
@@ -127,6 +128,15 @@ provide a custom timeout period using `--eval-timeout` argument. So if you face
 this error, the best option is to install Nodejs on your local system. If you
 can't then use the `--eval-timeout` argument and set a higher timeout value.
 
+### Fatal error occurs when executing a python command Line instruction as a job on python version 3.
+
+If your workflow creates a python command line instruction (like we do in this
+[unit test](https://github.com/common-workflow-language/cwltool/blob/master/tests/test_examples.py#L117) ) and you get a error `Fatal Python error: Failed to initialize Windows
+ random API (CryptoGen)` then try setting `SYSTEMROOT` environment variable to
+windows directory location (usually at `C:\\WINDOWS`). The reason behind this error
+is that when a python instance is created from current instance, it needs `SYSTEMROOT`
+env variable to starts its random generator on Windows OS.
+
 *If you still have problems with setting up and using Docker on Windows, please
 consult the online Docker Community. If the problem is specific to cwltool,
 create an [issue on cwltool](https://github.com/common-workflow-language/cwltool/issues).*