GH-83162: Rename re.error for better clarity. (#101677)

Renamed re.error for clarity, and kept re.error for backward compatibility.
Updated idlelib files at TJR's request.
---------

Co-authored-by: Matthias Bussonnier <mbussonnier@ucmerced.edu>
Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>
Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

3 files changed, 11 insertions, 7 deletions

diff --git a/Lib/re/__init__.py b/Lib/re/__init__.py
index 428d1b0..7e8abbf 100644
--- a/Lib/re/__init__.py
+++ b/Lib/re/__init__.py
@@ -117,7 +117,8 @@ A, L, and U are mutually exclusive.
     U  UNICODE     For compatibility only. Ignored for string patterns (it
                    is the default), and forbidden for bytes patterns.
 
-This module also defines an exception 'error'.
+This module also defines exception 'PatternError', aliased to 'error' for
+backward compatibility.
 
 """
 
@@ -133,7 +134,7 @@ __all__ = [
     "findall", "finditer", "compile", "purge", "escape",
     "error", "Pattern", "Match", "A", "I", "L", "M", "S", "X", "U",
     "ASCII", "IGNORECASE", "LOCALE", "MULTILINE", "DOTALL", "VERBOSE",
-    "UNICODE", "NOFLAG", "RegexFlag",
+    "UNICODE", "NOFLAG", "RegexFlag", "PatternError"
 ]
 
 __version__ = "2.2.1"
@@ -155,7 +156,7 @@ class RegexFlag:
     _numeric_repr_ = hex
 
 # sre exception
-error = _compiler.error
+PatternError = error = _compiler.PatternError
 
 # --------------------------------------------------------------------
 # public interface
diff --git a/Lib/re/_compiler.py b/Lib/re/_compiler.py
index f87712d..7b888f8 100644
--- a/Lib/re/_compiler.py
+++ b/Lib/re/_compiler.py
@@ -150,7 +150,7 @@ def _compile(code, pattern, flags):
                 if lo > MAXCODE:
                     raise error("looks too much behind")
                 if lo != hi:
-                    raise error("look-behind requires fixed-width pattern")
+                    raise PatternError("look-behind requires fixed-width pattern")
                 emit(lo) # look behind
             _compile(code, av[1], flags)
             emit(SUCCESS)
@@ -209,7 +209,7 @@ def _compile(code, pattern, flags):
             else:
                 code[skipyes] = _len(code) - skipyes + 1
         else:
-            raise error("internal: unsupported operand type %r" % (op,))
+            raise PatternError(f"internal: unsupported operand type {op!r}")
 
 def _compile_charset(charset, flags, code):
     # compile charset subprogram
@@ -235,7 +235,7 @@ def _compile_charset(charset, flags, code):
             else:
                 emit(av)
         else:
-            raise error("internal: unsupported set operator %r" % (op,))
+            raise PatternError(f"internal: unsupported set operator {op!r}")
     emit(FAILURE)
 
 def _optimize_charset(charset, iscased=None, fixup=None, fixes=None):
diff --git a/Lib/re/_constants.py b/Lib/re/_constants.py
index d8e483a..9c3c294 100644
--- a/Lib/re/_constants.py
+++ b/Lib/re/_constants.py
@@ -20,7 +20,7 @@ from _sre import MAXREPEAT, MAXGROUPS
 # SRE standard exception (access as sre.error)
 # should this really be here?
 
-class error(Exception):
+class PatternError(Exception):
     """Exception raised for invalid regular expressions.
 
     Attributes:
@@ -53,6 +53,9 @@ class error(Exception):
         super().__init__(msg)
 
 
+# Backward compatibility after renaming in 3.13
+error = PatternError
+
 class _NamedIntConstant(int):
     def __new__(cls, value, name):
         self = super(_NamedIntConstant, cls).__new__(cls, value)