python - QGIS corrupted processing tool

I've been dealing with various problems after re-installing QGIS and other GIS-related software (see QGIS corrupted plugins upon reinstallation).

The solution worked for a bout a day and now I lost the processing tool again. An other error message appeared when opening QGIS:

Impossible to load processing plugin provokes error when calling classFactory()

UnicodeDecodeError: 'ascii' codec can't decode byte 0xe9 in position 18: ordinal not in range(128)

Traceback (most recent call last):

  File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 306, in startPlugin
    plugins[packageName] = package.classFactory(iface)
  File "C:/Users/F�lix/.qgis2/python/plugins\processing\__init__.py", line 37, in classFactory
    from processing.ProcessingPlugin import ProcessingPlugin
  File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 572, in _import
    mod = _builtin_import(name, globals, locals, fromlist, level)
  File "C:/Users/F�lix/.qgis2/python/plugins\processing\ProcessingPlugin.py", line 47, in 
    if cmd_folder not in sys.path:
  File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 58, in showWarning
    "warning:%s\ntraceback:%s" % (warnings.formatwarning(message, category, filename, lineno), stk),

UnicodeDecodeError: 'ascii' codec can't decode byte 0xe9 in position 18: ordinal not in range(128)

Also, I have a second error when trying to re-install the processing extension through QGIS.

ImportError: cannot import name defaultOutputFolder

Traceback (most recent call last):
  File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 281, in loadPlugin
    __import__(packageName)
  File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 572, in _import
    mod = _builtin_import(name, globals, locals, fromlist, level)
  File "C:/Users/F�lix/.qgis2/python/plugins\processing\__init__.py", line 28, in 

    from processing.tools.dataobjects import *
  File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 572, in _import
    mod = _builtin_import(name, globals, locals, fromlist, level)
  File "C:/OSGEO4~1/apps/qgis/./python/plugins\processing\tools\dataobjects.py", line 35, in 
    from processing.core.ProcessingConfig import ProcessingConfig
  File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 572, in _import
    mod = _builtin_import(name, globals, locals, fromlist, level)
  File "C:/Users/F�lix/.qgis2/python/plugins\processing\core\ProcessingConfig.py", line 32, in 
    from processing.tools.system import defaultOutputFolder
ImportError: cannot import name defaultOutputFolder

Any ideas on how to solve this one?

Answer

One of the main culprits which forces a Unicode error is the user name. In this case:

"C:/Users/F�lix/...

Probably the best solution in these circumstances is to create a new user with a name which doesn't use characters with accents or similar symbols (i.e. Non-ASCII characters).