BF: recreates previous option of using trials.next() to advance trials

This had been lost in python futurize step in
GH-38740bcaff28d063f6519461d2780a3850886889

Closes GH-2322

Author: peircej

psychopy/data/staircase.py

@@ -393,6 +393,8 @@ def __next__(self):
         else:
             self._terminate()
 
+    next = __next__  # allows user to call without a loop `val = trials.next()`
+
     def _intensityInc(self):
         """increment the current intensity and reset counter
         """
@@ -1035,6 +1037,8 @@ def __next__(self):
         else:
             self._terminate()
 
+    next = __next__  # allows user to call without a loop `val = trials.next()`
+
     def _checkFinished(self):
         """checks if we are finished
         Updates attribute: `finished`
@@ -1242,6 +1246,8 @@ def __next__(self):
         else:
             self._terminate()
 
+    next = __next__  # allows user to call without a loop `val = trials.next()`
+
     def _checkFinished(self):
         """checks if we are finished
         Updates attribute: `finished`
@@ -1513,6 +1519,8 @@ def __next__(self):
         else:
             raise StopIteration
 
+    next = __next__  # allows user to call without a loop `val = trials.next()`
+
     def _startNewPass(self):
         """Create a new iteration of the running staircases for this pass.
 

psychopy/data/trial.py

@@ -362,6 +362,8 @@ def __next__(self):
             logging.exp(msg % vals, obj=self.thisTrial)
         return self.thisTrial
 
+    next = __next__  # allows user to call without a loop `val = trials.next()`
+
     def getFutureTrial(self, n=1):
         """Returns the condition for n trials into the future,
         without advancing the trials. A negative n returns a previous (past)
@@ -1020,6 +1022,8 @@ def __next__(self):
             logging.exp(msg % vals, obj=self.thisTrial)
         return self.thisTrial
 
+    next = __next__  # allows user to call without a loop `val = trials.next()`
+
     def getFutureTrial(self, n=1):
         """Returns the condition for n trials into the future, without
         advancing the trials. Returns 'None' if attempting to go beyond
@@ -1516,6 +1520,8 @@ def __next__(self):
             logging.exp(msg % vals, obj=self.thisTrial)
         return self.thisTrial
 
+    next = __next__  # allows user to call without a loop `val = trials.next()`
+
     def getCurrentTrialPosInDataHandler(self):
         # if there's no trial weights, then the current position is simply
         # [trialIndex, nRepetition]