Note: `PLW0101` remains in testing rather than preview, so this PR does
not modify any public behavior (hence the title beginning with
`internal` rather than `pylint`, for the sake of the changelog.)
Fixes an error in the processing of `try` statements in the control flow
graph builder.
When processing a try statement, the block following a `return` was
forced to point to the `finally` block. However, if the return was _in_
the `finally` block, this caused the block to point to itself. In the
case where the whole `try-finally` statement was also included inside of
a loop, this caused an infinite loop in the builder for the control flow
graph as it attempted to resolve edges.
Closes#15248
## Test function
### Source
```python
def l():
while T:
try:
while ():
if 3:
break
finally:
return
```
### Control Flow Graph
```mermaid
flowchart TD
start(("Start"))
return(("End"))
block0[["`*(empty)*`"]]
block1[["Loop continue"]]
block2["return\n"]
block3[["Loop continue"]]
block4["break\n"]
block5["if 3:
break\n"]
block6["while ():
if 3:
break\n"]
block7[["Exception raised"]]
block8["try:
while ():
if 3:
break
finally:
return\n"]
block9["while T:
try:
while ():
if 3:
break
finally:
return\n"]
start --> block9
block9 -- "T" --> block8
block9 -- "else" --> block0
block8 -- "Exception raised" --> block7
block8 -- "else" --> block6
block7 --> block2
block6 -- "()" --> block5
block6 -- "else" --> block2
block5 -- "3" --> block4
block5 -- "else" --> block3
block4 --> block2
block3 --> block6
block2 --> return
block1 --> block9
block0 --> return
```
