Revert "remove wrong warning"

Re-introduce a check for gamma and lambda fixed to different values in
case of equal asymptote experiments, but turning it into an Exception.
There's no way in this case to know what the user meant, so it safer
to bail out instead of guessing which parameter is to be trusted.

This reverts commit ec4e716.

psignifit/_configuration.py

@@ -139,6 +139,18 @@ def check_experiment_type_matches_fixed_parameters(self, fixed_params, experimen
             if fixed_params is not None and 'gamma' in fixed_params:
                 warnings.warn(
                     f'The parameter gamma was fixed to {fixed_params["gamma"]}. In {ExperimentType.N_AFC.value} experiments gamma is automatically fixed to 1/n. Ignoring fixed gamma.')
+        if experiment_type == ExperimentType.EQ_ASYMPTOTE.value:
+            if fixed_params is not None:
+                if 'gamma' in fixed_params:
+                    pass # we assume the user knows what they are doing
+                if 'lambda' in fixed_params:
+                    pass # we assume the user knows what they are doing
+                if 'lambda' in fixed_params and 'gamma' in fixed_params:
+                    if fixed_params['gamma'] != fixed_params['lambda']:
+                        raise PsignifitException(
+                            f'The parameters lambda {fixed_params["lambda"]} and'
+                            f' gamma {fixed_params["gamma"]} were fixed to different values.'
+                            f' In {experiment_type} experiments gamma and lambda need to be equal. ')
 
 
     def check_experiment_type(self, value):