tkuratomi bugfix for BOMs in powershell modules

fixes #15998

(cherry picked from commit 31e963dd2a)

lib/ansible/executor/module_common.py

@@ -668,6 +668,12 @@ def _find_snippet_imports(module_name, module_data, module_path, module_args, ta
         module_args_json = to_bytes(json.dumps(module_args))
         module_data = module_data.replace(REPLACER_JSONARGS, module_args_json)
 
+        # Powershell/winrm don't actually make use of shebang so we can
+        # safely set this here.  If we let the fallback code handle this
+        # it can fail in the presence of the UTF8 BOM commonly added by
+        # Windows text editors
+        shebang = u'#!powershell'
+
         # Sanity check from 1.x days.  This is currently useless as we only
         # get here if we are going to substitute powershell.ps1 into the
         # module anyway.  Leaving it for when/if we add other powershell