python/aws_cdk: synth lock file not released on python subprocess error

### Describe the bug

When `cdk synth` is run and the underlying Python code raises an Exception, e.g. due to a syntax error, the next run of synth fails with:

`Another CLI (PID=1) is currently synthing to cdk.out. Invoke the CLI in sequence, or use '--output' to synth into different directories.`

This appears to happen because the lock file in `cdk.out/synth.lock` is not released.

This is normally not noticed because the PID in the lock file is no longer live - https://github.com/aws/aws-cdk/blob/6d581d7d4a0107dc5acd532c603f90d253d8f72e/packages/aws-cdk/lib/api/util/rwlock.ts#L7 ; however when running CDK within a docker container then PIDs reoccur

### Expected Behavior

`cdk.out/synth.lock` is released

### Current Behavior

`cdk.out/synth.lock` is not released causing `Another CLI (PID=1) is currently synthing to cdk.out.
Invoke the CLI in sequence, or use '--output' to synth into different directories.`
to be raised on the next synth command unless the lock file is manually removed.

### Reproduction Steps

1. Add `assert 0` or something that will raise an exception in a Python CDK app
2. Run `cdk synth` for that app within docker
3. Run `cdk synth` again within docker and observe the issue because 2 and 3 have the same PID

### Possible Solution

_No response_

### Additional Information/Context

_No response_

### CDK CLI Version

2.72.1

### Framework Version

_No response_

### Node.js Version

18.13.0

### OS

Debian GNU/Linux 11

### Language

Python

### Language Version

_No response_

### Other information

_No response_

Start in packages/aws-cdk/lib/api/util/rwlock.ts and reproduce the failure with a Python CDK app inside Docker. Trace what happens to cdk.out/synth.lock when the Python subprocess raises an exception; done means a failed synth releases the lock and a second synth in the same container succeeds.

Written by the indexing model from the issue text.