Fix updating an existing script from a file

A `TypeError` occured when one tried to update an existing script from a
file.

This has been fixed.

modified:   CHANGES.rst
modified:   src/Products/PythonScripts/PythonScript.py
modified:   src/Products/PythonScripts/tests/testPythonScript.py

CHANGES.rst

@@ -3,6 +3,8 @@ Changelog
 
 4.12 (unreleased)
 -----------------
+- fix ``TypeError`` when updating an existing script from a file
+  (`#43 <https://github.com/zopefoundation/Products.PythonScripts/issues/43>`_)
 
 
 4.11 (2020-02-11)

src/Products/PythonScripts/PythonScript.py

@@ -195,6 +195,7 @@ def ZPythonScriptHTML_upload(self, REQUEST, file=''):
                     manage_tabs_message='No file specified',
                     manage_tabs_type='warning')
             file = file.read()
+            file = file.decode('utf-8')
 
         self.write(file)
         message = 'Saved changes.'

src/Products/PythonScripts/tests/testPythonScript.py

@@ -430,3 +430,11 @@ def test_ZPythonScriptHTML_upload__no_file(self):
         """It renders an error message if no file is uploaded."""
         self.browser.getControl('Upload File').click()
         self.assertIn('No file specified', self.browser.contents)
+
+    def test_ZPythonScriptHTML_upload__with_file(self):
+        file_contents = b'print("hello")'
+        self.browser.getControl('file').add_file(
+             file_contents, 'text/plain', 'script.py')
+        self.browser.getControl('Upload File').click()
+
+        assert 'Saved changes.' in self.browser.contents