Add a simple open wrapper for the bom python plugins to handle directory creation

eeschema/plugins/python_scripts/kicad_utils.py

@@ -0,0 +1,15 @@
+#
+# KiCad python module for some helper functions
+#
+
+import os
+
+def open_file_write(path, mode):
+    ''' Open "path" for writing, creating any parent directories as needed.
+    '''
+    dir_path = os.path.dirname(path)
+
+    if not os.path.isdir(dir_path):
+        os.makedirs(dir_path)
+
+    return open(path, mode)