replace string_type with str in easyblock.py

Author: boegel

easybuild/framework/easyblock.py

@@ -1413,7 +1413,7 @@ def make_module_extra(self, altroot=None, altversion=None):
             lines.append(self.module_generator.prepend_paths(key, value, allow_abs=self.cfg['allow_prepend_abs_path']))
 
         for (key, value) in self.cfg['modextrapaths_append'].items():
-            if isinstance(value, string_type):
+            if isinstance(value, str):
                 value = [value]
             elif not isinstance(value, (tuple, list)):
                 raise EasyBuildError("modextrapaths_append dict value %s (type: %s) is not a list or tuple",

test/framework/easyblock.py

@@ -1273,7 +1273,7 @@ def test_make_module_step(self):
                 self.assertEqual(num_prepends, 1, "Expected exactly 1 %s command in %s" % (regex.pattern, txt))
 
         for (key, vals) in modextrapaths_append.items():
-            if isinstance(vals, string_type):
+            if isinstance(vals, str):
                 vals = [vals]
             for val in vals:
                 if get_module_syntax() == 'Tcl':