Add validation of gen kw from runpath

src/ert/config/gen_kw_config.py

@@ -311,6 +311,10 @@ def _values_from_file(
             # internal order of sub-parameters:
             df = df.set_index(df.columns[0])
             return df.reindex(keys).values.flatten()
+        if not np.issubdtype(df.values.dtype, np.number):
+            raise ValueError(
+                f"The file {file_name} did not contain numbers, got {df.values.dtype}"
+            )
         return df.values.flatten()
 
     @staticmethod

tests/unit_tests/config/test_gen_kw_config.py

@@ -542,3 +542,20 @@ def test_gen_kw_config_validation():
                 ],
             }
         )
+
+
+def test_incorrect_values_in_forward_init_file_fails(tmp_path):
+    (tmp_path / "forward_init_1").write_text("incorrect", encoding="utf-8")
+    with pytest.raises(
+        ValueError,
+        match=f"{tmp_path / 'forward_init_1'} did not contain numbers, got object",
+    ):
+        GenKwConfig(
+            "GEN_KW",
+            True,
+            None,
+            None,
+            [],
+            str(tmp_path / "forward_init_%d"),
+            None,
+        ).read_from_runpath(tmp_path, 1)