fix(repl): fix repl server crash when meet a exception

[Hanaasagi]

Fixes #419.

This is a brief description.

1. fix the repl server crashed after exception
2. exec user code in independent context.
3. return exception info to client through the socket.

@mtshiba

[mtshiba]

Thank you!

[Hanaasagi]

@mtshiba Firstly, thank you for your correction. But there still exist some problems.

The following code uses sockets to send data to the client twice, although it involves two system calls. However, TCP is a stream-based protocol, so the client may receive the merged data while reading it sequentially.

erg/src/scripts/repl_server.py

Lines 47 to 53 in b444fca

	__client_socket.send('[Initialize]'.encode())
	__out = __sys.stdout.getvalue()[:-1]
	# assert not(__exc and __res)
	if __exc or __res:
	__out += '\n'
	__res = __out + __exc + __res
	__client_socket.send(__res.encode())

So there should be startswith , not match a string.

erg/src/dummy.rs

Lines 207 to 212 in b444fca

	match s {
	"[Exception] SystemExit" => Err(EvalErrors::from(EvalError::system_exit())),
	"[Initialize]" => {
	self.compiler.initialize_generator();
	self.read()
	}