Automatically retry flaky tests

See emscripten-core#19795

test/common.py

@@ -146,11 +146,26 @@ def decorated(self, *args, **kwargs):
   return decorated
 
 
-def flaky(note=''):
+def flaky(note='', retries=3):
   assert not callable(note)
+
   if EMTEST_SKIP_FLAKY:
     return unittest.skip(note)
-  return lambda f: f
+
+  def decorated(f):
+    @wraps(f)
+    def modified(*args, **kwargs):
+      for i in range(retries):
+        try:
+          return f(*args, **kwargs)
+        except AssertionError as exc:
+          preserved_exc = exc
+          logging.info(f'Retrying flaky test (attempt {i}/{retries} failed): {exc}')
+      raise AssertionError('Flaky test has failed too many times') from preserved_exc
+
+    return modified
+
+  return decorated
 
 
 def disabled(note=''):
@@ -288,6 +303,7 @@ def with_env_modify(updates):
   assert not callable(updates)
 
   def decorated(f):
+    @wraps(f)
     def modified(self, *args, **kwargs):
       with env_modify(updates):
         return f(self, *args, **kwargs)