Syntax errors from django migration to v5 (more strict regex validation?)

[lubojr]

Two more warnings appear in the renderer startup on first request:

/opt/eoxserver/eoxserver/resources/coverages/formats.py:421: SyntaxWarning: invalid escape sequence '\w'
_gerexValMime = re.compile("^[\w][-\w]/[\w][-+\w](;[-\w]=[-\w])$")
/opt/eoxserver/eoxserver/resources/coverages/formats.py:424: SyntaxWarning: invalid escape sequence '\w'
_gerexValDriv = re.compile("^[\w][-\w]/[\w][-\w]*$")