DOC Improve the error message in TSNE to include the problematic values (scikit-learn#30876)

Co-authored-by: Stefanie Senger <91849487+StefanieSenger@users.noreply.github.com>

Author: frewsxcv

sklearn/manifold/_t_sne.py

@@ -859,7 +859,10 @@ def __init__(
 
     def _check_params_vs_input(self, X):
         if self.perplexity >= X.shape[0]:
-            raise ValueError("perplexity must be less than n_samples")
+            raise ValueError(
+                f"perplexity ({self.perplexity}) must be less "
+                f"than n_samples ({X.shape[0]})"
+            )
 
     def _fit(self, X, skip_num_points=0):
         """Private function to fit the model using X as training data."""

sklearn/manifold/tests/test_t_sne.py

@@ -1,3 +1,4 @@
+import re
 import sys
 from io import StringIO
 
@@ -1170,7 +1171,7 @@ def test_tsne_perplexity_validation(perplexity):
         perplexity=perplexity,
         random_state=random_state,
     )
-    msg = "perplexity must be less than n_samples"
+    msg = re.escape(f"perplexity ({perplexity}) must be less than n_samples (20)")
     with pytest.raises(ValueError, match=msg):
         est.fit_transform(X)