Emit tracing output to stderr

Behavior of the crate differs between the log and tracing backends:
while log defaults to printing messages to stderr, tracing emits them to
stdout. Until version 0.3.19 the tracing-subscriber crate did not allow
changing this default. Pull request #3187 [0] changed that and release
0.3.20 contains this logic.
Now that we can, adjust the tracing based backend to log to stderr for
consistency.

[0] tokio-rs/tracing#3187

Author: d-e-s-o

Cargo.toml

@@ -78,7 +78,7 @@ unstable = ["test-log-macros/unstable"]
 
 [dependencies]
 test-log-macros = {version = "0.2.18", path = "macros"}
-tracing-subscriber = {version = "0.3.17", default-features = false, optional = true, features = ["env-filter", "fmt"]}
+tracing-subscriber = {version = "0.3.20", default-features = false, optional = true, features = ["env-filter", "fmt"]}
 env_logger = {version = "0.11", default-features = false, optional = true}
 
 [dev-dependencies]

macros/src/lib.rs

@@ -208,6 +208,7 @@ fn expand_logging_init(attribute_args: &AttributeArgs) -> Tokens {
           ::test_log::env_logger::Env::default()
             .default_filter_or(#default_filter)
         )
+        .target(::test_log::env_logger::Target::Stderr)
         .is_test(true)
         .try_init();
     }
@@ -274,7 +275,7 @@ fn expand_tracing_init(attribute_args: &AttributeArgs) -> Tokens {
       let _ = ::test_log::tracing_subscriber::FmtSubscriber::builder()
         .with_env_filter(#env_filter)
         .with_span_events(__internal_event_filter)
-        .with_test_writer()
+        .with_writer(::test_log::tracing_subscriber::fmt::TestWriter::with_stderr)
         .try_init();
     }
   }