assertion: _notin_text: handle non-printable characters

Ref: pytest-dev#6702

src/_pytest/assertion/util.py

@@ -498,21 +498,31 @@ def _compare_eq_cls(
 
 
 def _notin_text(term: str, text: str, verbose: int = 0) -> List[str]:
+    from wcwidth import wcwidth
+
     index = text.find(term)
     head = text[:index]
     tail = text[index + len(term) :]
     correct_text = head + tail
-    diff = _diff_text(correct_text, text, verbose)
+
     newdiff = ["%s is contained here:" % saferepr(term, maxsize=42)]
-    for line in diff:
-        if line.startswith("Skipping"):
-            continue
-        if line.startswith("- "):
-            continue
-        if line.startswith("+ "):
-            newdiff.append("  " + line[2:])
-        else:
-            newdiff.append(line)
+    if any(
+        wcwidth(ch) <= 0
+        for ch in [ch for lines in [term, correct_text] for ch in lines]
+    ):
+        newdiff = [
+            "NOTE: Strings contain non-printable characters. Escaping them using repr()."
+        ] + newdiff
+        text = repr(text)
+        indent = " " * (index + 1)
+        marker = "+" * (len(repr(term)) - 2)
+    else:
+        indent = " " * index
+        marker = "+" * len(term)
+    newdiff += [
+        "  " + text,
+        "? " + indent + marker,
+    ]
     return newdiff
 
 

testing/test_assertion.py

@@ -1200,6 +1200,16 @@ def test_reprcompare_notin() -> None:
     ]
 
 
+def test_reprcompare_notin_newline() -> None:
+    assert callop("not in", "foo\n", "aaafoo\nbbb") == [
+        r"'foo\n' not in 'aaafoo\nbbb'",
+        r"NOTE: Strings contain non-printable characters. Escaping them using repr().",
+        r"'foo\n' is contained here:",
+        r"  'aaafoo\nbbb'",
+        r"?     +++++",
+    ]
+
+
 def test_reprcompare_whitespaces():
     config = mock_config()
     detail = plugin.pytest_assertrepr_compare(config, "==", "\r\n", "\n")