Generalize RecursionError handling.

There are many functions that are implemented using recursion besides
TokenList.flatten() that could raise RecursionError.  Move the
try/except block handling RecursionError from TokenList.flatten() to
FilterStack.run() to avoid any of them resulting in an unwanted
RecursionError.

sqlparse/engine/filter_stack.py

@@ -10,6 +10,7 @@
 from sqlparse import lexer
 from sqlparse.engine import grouping
 from sqlparse.engine.statement_splitter import StatementSplitter
+from sqlparse.exceptions import SQLParseError
 from sqlparse.filters import StripTrailingSemicolonFilter
 
 
@@ -26,22 +27,25 @@ def enable_grouping(self):
         self._grouping = True
 
     def run(self, sql, encoding=None):
-        stream = lexer.tokenize(sql, encoding)
-        # Process token stream
-        for filter_ in self.preprocess:
-            stream = filter_.process(stream)
+        try:
+            stream = lexer.tokenize(sql, encoding)
+            # Process token stream
+            for filter_ in self.preprocess:
+                stream = filter_.process(stream)
 
-        stream = StatementSplitter().process(stream)
+            stream = StatementSplitter().process(stream)
 
-        # Output: Stream processed Statements
-        for stmt in stream:
-            if self._grouping:
-                stmt = grouping.group(stmt)
+            # Output: Stream processed Statements
+            for stmt in stream:
+                if self._grouping:
+                    stmt = grouping.group(stmt)
 
-            for filter_ in self.stmtprocess:
-                filter_.process(stmt)
+                for filter_ in self.stmtprocess:
+                    filter_.process(stmt)
 
-            for filter_ in self.postprocess:
-                stmt = filter_.process(stmt)
+                for filter_ in self.postprocess:
+                    stmt = filter_.process(stmt)
 
-            yield stmt
+                yield stmt
+        except RecursionError as err:
+            raise SQLParseError('Maximum recursion depth exceeded') from err

sqlparse/sql.py

@@ -10,7 +10,6 @@
 import re
 
 from sqlparse import tokens as T
-from sqlparse.exceptions import SQLParseError
 from sqlparse.utils import imt, remove_quotes
 
 
@@ -211,14 +210,11 @@ def flatten(self):
 
         This method is recursively called for all child tokens.
         """
-        try:
-            for token in self.tokens:
-                if token.is_group:
-                    yield from token.flatten()
-                else:
-                    yield token
-        except RecursionError as err:
-            raise SQLParseError('Maximum recursion depth exceeded') from err
+        for token in self.tokens:
+            if token.is_group:
+                yield from token.flatten()
+            else:
+                yield token
 
     def get_sublists(self):
         for token in self.tokens: