*Really* fix completion with multiple words.

Turns out re.escape also escapes spaces, so we'd need to replace '(\\ )'
groups after escaping. At this point it's easier to just combine spaces
before escaping the pattern.

Fixes #1934.
Supersedes #1935.

qutebrowser/completion/models/sortfilter.py

@@ -68,8 +68,9 @@ class CompletionFilterModel(QSortFilterProxyModel):
         """
         with debug.log_time(log.completion, 'Setting filter pattern'):
             self.pattern = val
+            val = re.sub(r' +', r' ', val)  # See #1919
             val = re.escape(val)
-            val = re.sub(r'\ +', r'.*', val)
+            val = val.replace(r'\ ', '.*')
             self.pattern_re = re.compile(val, re.IGNORECASE)
             self.invalidate()
             sortcol = 0

tests/unit/completion/test_sortfilter.py

@@ -64,6 +64,8 @@ def _extract_model_data(model):
     ('foo', 'barfoobar', True),
     ('foo bar', 'barfoobar', True),
     ('foo   bar', 'barfoobar', True),
+    ('foo bar', 'barfoobazbar', True),
+    ('foo   bar', 'barfoobazbar', True),
     ('foo', 'barFOObar', True),
     ('Foo', 'barfOObar', True),
     ('ab', 'aonebtwo', False),