fixing mypy error

Author: kapilkd13

cwltool/builder.py

@@ -62,7 +62,7 @@ def __init__(self):  # type: () -> None
         self.job_script_provider = None  # type: Any
 
     def build_job_script(self, commands):
-        # type: (List[str]) -> Text
+        # type: (Union[List[str],List[bytes]]) -> Text
         build_job_script_method = getattr(self.job_script_provider, "build_job_script", None)  # type: Callable[[Builder, List[str]], Text]
         if build_job_script_method:
             return build_job_script_method(self, commands)

cwltool/job.py

@@ -424,7 +424,7 @@ def run(self, pull_image=True, rm_container=True,
 
 
 def _job_popen(
-        commands,  # type: List[str]
+        commands,  # type: Union[List[str],List[bytes]]
         stdin_path,  # type: Text
         stdout_path,  # type: Text
         stderr_path,  # type: Text