Improve error reporting of invalid UTF-8 when deserializing strings
std::io::Read read_to_string() [1] reports this uninformative error:
thread 'main' panicked at 'Err: IOError(Custom { kind: InvalidData, error: StringError("stream did not contain valid UTF-8") })', src/server/mod.rs:442:33
Instead of read_to_string(), use read_to_end() to read into a buffer,
then convert using String::from_utf8() and unwrap it. This gives a
better error message when UTF-8 fails to decode:
thread '' panicked at 'called Result::unwrap() on an Err value: FromUtf8Error { bytes: [105, 110, 101, 99, 114, 97, 102, 116, 58, 99, 114, 97, 102, 116, 105, 110, 103, 95, 115, 104, 97, 112, 101, 100, 20, 109, 105, 110, 101, 99, 114, 97, 102, 116, 58, 98, 111, 110, 101, 95, 98, 108, 111, 99, 107, 3, 3, 0, 1, 1, 134, 5, 1, 0, 1, 1, 134, 5, 1, 0, 1, 1, 134, 5, 1, 0, 1, 1, 134, 5, 1, 0, 1, 1, 134, 5, 1, 0, 1, 1, 134, 5, 1, 0, 1, 1, 134, 5, 1, 0, 1, 1, 134, 5, 1, 0, 1, 1, 134, 5, 1, 0, 1, 249, 2, 1, 0, 25, 109], error: Utf8Error { valid_up_to: 50, error_len: Some(1) } }', src/libcore/result.rs:1009:5
which is helpful for tracking down protocol errors, such as updating to
a new protocol (developed for GH-132 / GH-72).
[1] https://doc.rust-lang.org/nightly/std/io/trait.Read.html#method.read_to_string
[2] https://doc.rust-lang.org/std/string/struct.String.html#method.from_utf8
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