rust-ext: consistently and properly define hint argument to readline()

The `#[args()]` annotation used the wrong argument name. And in one
case this argument was not accepted.

Found this as part of attempting to to upgrade PyO3 to 0.18, which
complained at run-time about `hint` being a required argument.

Author: indygreg

rust-ext/src/compression_reader.rs

@@ -157,7 +157,9 @@ impl ZstdCompressionReader {
         Err(PyErr::from_instance(exc))
     }
 
-    fn readlines(&self, py: Python) -> PyResult<()> {
+    #[args(hint = "None")]
+    #[allow(unused_variables)]
+    fn readlines(&self, py: Python, hint: Option<&PyAny>) -> PyResult<()> {
         let io = py.import("io")?;
         let exc = io.getattr("UnsupportedOperation")?;
 

rust-ext/src/compression_writer.rs

@@ -145,7 +145,7 @@ impl ZstdCompressionWriter {
         Err(PyErr::from_instance(exc))
     }
 
-    #[args(size = "None")]
+    #[args(hint = "None")]
     #[allow(unused_variables)]
     fn readlines(&self, py: Python, hint: Option<&PyAny>) -> PyResult<()> {
         let io = py.import("io")?;

rust-ext/src/decompression_reader.rs

@@ -137,7 +137,7 @@ impl ZstdDecompressionReader {
         Err(PyErr::from_instance(exc))
     }
 
-    #[args(size = "None")]
+    #[args(hint = "None")]
     #[allow(unused_variables)]
     fn readlines(&self, py: Python, hint: Option<&PyAny>) -> PyResult<()> {
         let io = py.import("io")?;

rust-ext/src/decompression_writer.rs

@@ -150,7 +150,7 @@ impl ZstdDecompressionWriter {
         Err(PyErr::from_instance(exc))
     }
 
-    #[args(size = "None")]
+    #[args(hint = "None")]
     #[allow(unused_variables)]
     fn readlines(&self, py: Python, hint: Option<&PyAny>) -> PyResult<()> {
         let io = py.import("io")?;