hack rand down for rustc 1.8

.travis.yml

@@ -7,9 +7,11 @@ matrix:
   include:
     - rust: 1.8.0
       before_script:
-        # libc 0.2.34 started using #[deprecated]
+        # rand 0.3.22 started depending on rand 0.4, which requires rustc 1.15
+        # manually hacking the lockfile due to the limitations of cargo#2773
         - cargo generate-lockfile
-        - cargo update --package libc --precise 0.2.33
+        - sed -i -e 's/"rand 0.[34].[0-9]\+/"rand 0.3.20/' Cargo.lock
+        - sed -i -e '/^name = "rand"/,/^$/s/version = "0.3.[0-9]\+"/version = "0.3.20"/' Cargo.lock
 sudo: false
 script:
   - cargo build --verbose

ci/rustup.sh

@@ -8,9 +8,11 @@ export TRAVIS_RUST_VERSION
 for TRAVIS_RUST_VERSION in 1.8.0 stable beta nightly; do
     run="rustup run $TRAVIS_RUST_VERSION"
     if [ "$TRAVIS_RUST_VERSION" = 1.8.0 ]; then
-      # libc 0.2.34 started using #[deprecated]
+      # rand 0.3.22 started depending on rand 0.4, which requires rustc 1.15
+      # manually hacking the lockfile due to the limitations of cargo#2773
       $run cargo generate-lockfile
-      $run cargo update --package libc --precise 0.2.33 || :
+      $run sed -i -e 's/"rand 0.[34].[0-9]\+/"rand 0.3.20/' Cargo.lock
+      $run sed -i -e '/^name = "rand"/,/^$/s/version = "0.3.[0-9]\+"/version = "0.3.20"/' Cargo.lock
     fi
     $run cargo build --verbose
     $run $PWD/ci/test_full.sh