ccmlib/node.py: _do_run_nodetool(): filter out debug-mode warnings fr…

…om stderr

These messages are printed by seastar and ASAN respectively and they
trigger tests which look for error messages in stderr. Filter them out
to address this problem at the root, instead of dealing with it in each
individual test.

ccmlib/node.py

@@ -826,7 +826,22 @@ def _do_run_nodetool(self, nodetool, capture_output=True, wait=True, timeout=Non
             if exit_status != 0:
                 raise NodetoolError(" ".join(nodetool), exit_status, stdout, stderr)
 
-        return stdout, stderr
+        ignored_patterns = (re.compile("WARNING: debug mode. Not for benchmarking or production"),
+                            re.compile("==[0-9]+==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!"))
+
+        def keep(line):
+            self.debug(f"checking {line}")
+            for ignored_pattern in ignored_patterns:
+                if ignored_pattern.fullmatch(line):
+                    return False
+            return True
+
+        def filter_debug_errors(stderr):
+            if stderr is None:
+                return stderr
+            return '\n'.join([line for line in stderr.split('\n') if keep(line)])
+
+        return stdout, filter_debug_errors(stderr)
 
     def nodetool(self, cmd, capture_output=True, wait=True, timeout=None, verbose=True):
         """