scripts: Replace basestring -> str for python3

Python 3 doesn't have basestring type as all string
are unicode strings.

(From OE-Core rev: e8cfab060f4ff3c4c16387871354d407910e87aa)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/scriptutils.py

@@ -103,7 +103,7 @@ def fetch_uri(d, uri, destdir, srcrev=None):
     return ret
 
 def run_editor(fn):
-    if isinstance(fn, basestring):
+    if isinstance(fn, str):
         params = '"%s"' % fn
     else:
         params = ''