[orange] Fix StringIO import to be compatible with python3

With this fix, the module still works with python 2.7
12 jobs for master in 1 minute and 16 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
failed #23679
build:2.7

00:00:55

failed #23680
build:3

00:01:16

 
  Test
skipped #23682
allowed to fail
lint:2.7
skipped #23686
allowed to fail
lint:3
skipped #23681
pyflakes:2.7
skipped #23685
pyflakes:3
skipped #23683
unittests:2.7
skipped #23687
unittests:3
skipped #23684
allowed to fail
unittests-modules:2.7
skipped #23688
allowed to fail
unittests-modules:3
 
  Deploy
skipped #23689
doc:2.7
skipped #23690
doc:3
 
Name Stage Failure
failed
build:2.7 Build
  File "./tools/local_install.py", line 30, in <module>
subprocess.check_call([sys.executable, os.path.join(dest, 'weboob-config'), 'update'])
File "/usr/local/lib/python2.7/subprocess.py", line 190, in check_call
Weboob local installer

Installing weboob applications into ‘/root/bin’.
raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['/usr/local/bin/python2', '/root/bin/weboob-config', 'update']' returned non-zero exit status 130
ERROR: Job failed: exit code 1
failed
build:3 Build

Installing weboob applications into ‘/root/bin’.
Traceback (most recent call last):
File "./tools/local_install.py", line 30, in <module>
subprocess.check_call([sys.executable, os.path.join(dest, 'weboob-config'), 'update'])
File "/usr/local/lib/python3.8/subprocess.py", line 364, in check_call
raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['/usr/local/bin/python3', '/root/bin/weboob-config', 'update']' returned non-zero exit status 130.
ERROR: Job failed: exit code 1