Also pin pyo3 dependecy to 0.5.0 for now

Author: rth

Cargo.toml

@@ -15,7 +15,7 @@ libc = "0.2.43"
 num-complex = "0.2.1"
 num-traits = "0.2.6"
 ndarray = "0.12.0"
-pyo3 = "0.5.0"
+pyo3 = "= 0.5.0"
 
 [features]
 # In default setting, python version is automatically detected