diff --git a/.travis.yml b/.travis.yml
index 969a16cceb3..ba205f0d9fa 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -23,20 +23,6 @@ matrix:
       rust: beta
       if: branch != master OR type = pull_request
 
-    # Minimum Rust supported channel. We enable these to make sure we
-    # continue to work on the advertised minimum Rust version.
-    # However cargo only supports the latest stable so this will get
-    # increased every 6 weeks or so when the first PR to use a new feature.
-    - env: TARGET=x86_64-unknown-linux-gnu
-           ALT=i686-unknown-linux-gnu
-      rust: 1.31.0
-      script:
-        - rustup toolchain install nightly || travis_terminate 1
-        - cargo +nightly generate-lockfile -Z minimal-versions || travis_terminate 1
-        - cargo -V || travis_terminate 1
-        - cargo test --features=deny-warnings || travis_terminate 1
-      if: branch != master OR type = pull_request
-
     - env: TARGET=x86_64-unknown-linux-gnu
            ALT=i686-unknown-linux-gnu
       rust: nightly
diff --git a/appveyor.yml b/appveyor.yml
index e05d4791672..5d2ec309b8a 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -2,9 +2,6 @@ environment:
   matrix:
   - TARGET: x86_64-pc-windows-msvc
     OTHER_TARGET: i686-pc-windows-msvc
-  - TARGET: x86_64-pc-windows-msvc
-    MINIMAL_VERSIONS: true
-    CFG_DISABLE_CROSS_TESTS: 1
 
 install:
   - if NOT defined APPVEYOR_PULL_REQUEST_NUMBER if "%APPVEYOR_REPO_BRANCH%" == "master" appveyor exit
diff --git a/src/cargo/util/errors.rs b/src/cargo/util/errors.rs
index fb50157ff50..a3f071c9fe5 100644
--- a/src/cargo/util/errors.rs
+++ b/src/cargo/util/errors.rs
@@ -307,7 +307,6 @@ pub fn process_error(
 
     #[cfg(unix)]
     fn status_to_string(status: ExitStatus) -> String {
-        use libc;
         use std::os::unix::process::*;
 
         if let Some(signal) = status.signal() {
diff --git a/src/cargo/util/paths.rs b/src/cargo/util/paths.rs
index 961ded48c97..00ee3f5ce1b 100644
--- a/src/cargo/util/paths.rs
+++ b/src/cargo/util/paths.rs
@@ -217,7 +217,6 @@ pub fn path2bytes(path: &Path) -> CargoResult<&[u8]> {
 
 #[cfg(unix)]
 pub fn bytes2path(bytes: &[u8]) -> CargoResult<PathBuf> {
-    use std::ffi::OsStr;
     use std::os::unix::prelude::*;
     Ok(PathBuf::from(OsStr::from_bytes(bytes)))
 }
diff --git a/src/crates-io/Cargo.toml b/src/crates-io/Cargo.toml
index dddac0d5cc1..042333347e0 100644
--- a/src/crates-io/Cargo.toml
+++ b/src/crates-io/Cargo.toml
@@ -16,6 +16,7 @@ path = "lib.rs"
 [dependencies]
 curl = "0.4"
 failure = "0.1.1"
+http = "0.1"
 serde = { version = "1.0", features = ['derive'] }
 serde_derive = "1.0"
 serde_json = "1.0"
diff --git a/src/crates-io/lib.rs b/src/crates-io/lib.rs
index 342442519a5..1b4d860d692 100644
--- a/src/crates-io/lib.rs
+++ b/src/crates-io/lib.rs
@@ -8,6 +8,7 @@ use std::io::Cursor;
 
 use curl::easy::{Easy, List};
 use failure::bail;
+use http::status::StatusCode;
 use serde::{Deserialize, Serialize};
 use serde_json;
 use url::percent_encoding::{percent_encode, QUERY_ENCODE_SET};
@@ -323,30 +324,31 @@ fn handle(handle: &mut Easy, read: &mut dyn FnMut(&mut [u8]) -> usize) -> Result
         handle.perform()?;
     }
 
-    match handle.response_code()? {
-        0 => {} // file upload url sometimes
-        200 => {}
-        403 => bail!("received 403 unauthorized response code"),
-        404 => bail!("received 404 not found response code"),
-        code => bail!(
+    let body = match String::from_utf8(body) {
+        Ok(body) => body,
+        Err(..) => bail!("response body was not valid utf-8"),
+    };
+    let errors = serde_json::from_str::<ApiErrorList>(&body).ok().map(|s| {
+        s.errors.into_iter().map(|s| s.detail).collect::<Vec<_>>()
+    });
+
+    match (handle.response_code()?, errors) {
+        (0, None) | (200, None) => {},
+        (code, Some(errors)) => {
+            let code = StatusCode::from_u16(code as _)?;
+            bail!("api errors (status {}): {}", code, errors.join(", "))
+        }
+        (code, None) => bail!(
             "failed to get a 200 OK response, got {}\n\
              headers:\n\
              \t{}\n\
              body:\n\
              {}",
-            code,
-            headers.join("\n\t"),
-            String::from_utf8_lossy(&body)
+             code,
+             headers.join("\n\t"),
+             body,
         ),
     }
 
-    let body = match String::from_utf8(body) {
-        Ok(body) => body,
-        Err(..) => bail!("response body was not valid utf-8"),
-    };
-    if let Ok(errors) = serde_json::from_str::<ApiErrorList>(&body) {
-        let errors = errors.errors.into_iter().map(|s| s.detail);
-        bail!("api errors: {}", errors.collect::<Vec<_>>().join(", "));
-    }
     Ok(body)
 }
diff --git a/tests/testsuite/death.rs b/tests/testsuite/death.rs
index 98316860b3e..2afddf64ae1 100644
--- a/tests/testsuite/death.rs
+++ b/tests/testsuite/death.rs
@@ -131,8 +131,6 @@ fn ctrl_c_kills_everyone() {
 
 #[cfg(unix)]
 fn ctrl_c(child: &mut Child) {
-    use libc;
-
     let r = unsafe { libc::kill(-(child.id() as i32), libc::SIGINT) };
     if r < 0 {
         panic!("failed to kill: {}", io::Error::last_os_error());