travis-ci: switch to trusty; cache pip packages

This applies several changes to the non-docker travis-ci builds:

- Make all builds use trusty rather than precise.  pybind can't really
  build in precise anyway (we install essentially the entire toolchain
  backported from trusty on every build), and so this saves needing to
  install all the backported packages during the build setup.
- Updated the 3.5 build to 3.6 (via deadsnakes, which didn't backport
  3.6 to ubuntu releases earlier than trusty).
- As a result of the switch to trusty, the BAREBONES build now picks up
  the (default installed) python 3.5 installation.
- Invoke pip everywhere via $PYTHON -m pip rather than the pip
  executable, which saves us having to figure out what the pip
  executable is, and ensures that we are using the correct pip.
- Install packages with `pip --user` rather than in a virtualenv.
- Add the local user python package archive to the travis-ci cache
  (rather than the pip cache).  This saves needing to install packages
  during installation (unless there are updates, in which case the
  package and the cache are updated).
- Install numpy and scipy on the pypy build.  This has to build from
  source (and so blas and fortran need to be installed on the build),
  but given the above caching, the build will only be slow for the first
  build after a new numpy/scipy release.  This testing is valuable:
  numpy has various behaviour differences under pypy.
- Added set -e/+e around the before_install/install blocks so that a
  failure here (e.g. a pip install failure or dependency download
  failure) triggers a build failure.
- Update eigen version to latest (3.3.3), mainly to be consistent with
  the appveyor build.
- The travis trusty environment has an upgraded cmake, so this
  downgrades cmake (to the stock trusty version) on the first couple
  jobs so that we're still including some cmake 2.8.12 testing.

.travis.yml

@@ -1,4 +1,5 @@
 language: cpp
+dist: trusty
 sudo: false
 matrix:
   include:
@@ -6,14 +7,13 @@ matrix:
     env: PYTHON=2.7 CPP=11 GCC=4.8
     addons:
       apt:
-        sources: [ubuntu-toolchain-r-test, kubuntu-backports]
-        packages: [g++-4.8, cmake]
+        packages: [cmake=2.\*, cmake-data=2.\*]
   - os: linux
-    env: PYTHON=3.5 CPP=11 GCC=4.8
+    env: PYTHON=3.6 CPP=11 GCC=4.8
     addons:
       apt:
-        sources: [ubuntu-toolchain-r-test, kubuntu-backports, deadsnakes]
-        packages: [g++-4.8, cmake, python3.5-dev]
+        sources: [deadsnakes]
+        packages: [python3.6-dev python3.6-venv, cmake=2.\*, cmake-data=2.\*]
   - sudo: true
     services: docker
     env: PYTHON=2.7 CPP=14 GCC=6
@@ -34,11 +34,10 @@ matrix:
     env: PYTHON=3.6 CPP=14 CLANG
   # Test a PyPy 2.7 build
   - os: linux
-    dist: trusty
     env: PYPY=5.7 PYTHON=2.7 CPP=11 GCC=4.8
     addons:
       apt:
-        packages: [g++-4.8, cmake]
+        packages: [libblas-dev, liblapack-dev, gfortran]
   - sudo: true
     services: docker
     env: ARCH=i386 PYTHON=3.5 CPP=14 GCC=6
@@ -58,22 +57,19 @@ matrix:
   # A barebones build makes sure everything still works without optional deps (numpy/scipy/eigen)
   # and also tests the automatic discovery functions in CMake (Python version, C++ standard).
   - os: linux
-    env: BAREBONES
-    addons:
-      apt:
-        sources: [ubuntu-toolchain-r-test, kubuntu-backports]
-        packages: [g++-4.8, cmake]
-    install: pip install pytest
+    env: BAREBONES PYTHON=3.5
+    install: $PY_CMD -m pip install --user --upgrade pytest
   # Documentation build:
   - os: linux
     language: docs
     env: DOCS STYLE LINT
     install:
-    - pip install --upgrade sphinx sphinx_rtd_theme flake8 pep8-naming
+    - export PATH="~/.local/bin:$PATH"
+    - $PY_CMD -m pip install --user --upgrade sphinx sphinx_rtd_theme flake8 pep8-naming
     - |
       curl -fsSL ftp://ftp.stack.nl/pub/users/dimitri/doxygen-1.8.12.linux.bin.tar.gz | tar xz
       export PATH="$PWD/doxygen-1.8.12/bin:$PATH"
-      pip install https://github.com/michaeljones/breathe/archive/master.zip
+      $PY_CMD -m pip install --user --upgrade https://github.com/michaeljones/breathe/archive/master.zip
     script:
     - make -C docs html SPHINX_OPTIONS=-W
     - tools/check-style.sh
@@ -83,8 +79,9 @@ matrix:
     - env: PYTHON=3.5 CPP=17 CLANG=4.0
 cache:
   directories:
-  - $HOME/.cache/pip
-  - $HOME/Library/Caches/pip
+  - $HOME/.local/bin
+  - $HOME/.local/lib
+  - $HOME/Library/Python
 before_install:
 - |
   # Configure build variables
@@ -107,18 +104,11 @@ before_install:
   fi
   if [ -n "$CPP" ]; then export CPP=-std=c++$CPP; fi
   if [ "${PYTHON:0:1}" = "3" ]; then export PY=3; fi
-  if [ "$PYPY" = "5.7" ]; then
-    curl -fSL https://bitbucket.org/pypy/pypy/downloads/pypy2-v5.7.0-linux64.tar.bz2 | tar -xj
-    export PYPY_BINARY=$(echo `pwd`/pypy2-v5.7.0-linux64/bin/pypy)
-    export CMAKE_EXTRA_ARGS="-DPYTHON_EXECUTABLE:FILEPATH=$PYPY_BINARY"
-  fi
   if [ -n "$DEBUG" ]; then export CMAKE_EXTRA_ARGS="-DCMAKE_BUILD_TYPE=Debug"; fi
 - |
   # Initialize environment
-  if [ -n "$PYPY" ]; then
-    $PYPY_BINARY -m ensurepip
-    $PYPY_BINARY -m pip install pytest
-  elif [ -n "$DOCKER" ]; then
+  set -e
+  if [ -n "$DOCKER" ]; then
     docker pull $DOCKER
 
     export containerid=$(docker run --detach --tty \
@@ -130,24 +120,30 @@ before_install:
     export SCRIPT_RUN_PREFIX="docker exec --tty $containerid"
     $SCRIPT_RUN_PREFIX sh -c 'for s in 0 15; do sleep $s; apt-get update && apt-get -qy dist-upgrade && break; done'
   else
-    if [ "$TRAVIS_OS_NAME" = "linux" ]; then
-      pip install --user --upgrade pip virtualenv
-      virtualenv -p python$PYTHON venv
-    elif [ "$TRAVIS_OS_NAME" = "osx" ]; then
-      if [ "$PY" = "3" ]; then
-        brew update; brew install python$PY;
-      else
-        curl -fsSL -O https://bootstrap.pypa.io/get-pip.py
-        sudo -H python get-pip.py
+    if [ "$PYPY" = "5.7" ]; then
+      curl -fSL https://bitbucket.org/pypy/pypy/downloads/pypy2-v5.7.1-linux64.tar.bz2 | tar -xj
+      export PY_CMD=$(echo `pwd`/pypy2-v5.7.1-linux64/bin/pypy)
+      export CMAKE_EXTRA_ARGS="-DPYTHON_EXECUTABLE:FILEPATH=$PY_CMD"
+    else
+      export PY_CMD=python$PYTHON
+      if [ "$TRAVIS_OS_NAME" = "osx" ]; then
+        if [ "$PY" = "3" ]; then
+          brew update; brew install python$PY;
+        else
+          curl -fsSL https://bootstrap.pypa.io/get-pip.py | $PY_CMD - --user
+        fi
       fi
-      pip$PY install --user --upgrade pip virtualenv
-      python$PY -m virtualenv venv
     fi
-    source venv/bin/activate
+    if [ "$PY" = 3 ] || [ -n "$PYPY" ]; then
+      $PY_CMD -m ensurepip --user
+    fi
+    $PY_CMD -m pip install --user --upgrade pip wheel
   fi
+  set +e
 install:
 - |
   # Install dependencies
+  set -e
   if [ -n "$DOCKER" ]; then
     if [ -n "$DEBUG" ]; then
       PY_DEBUG="python$PY-dbg python$PY-scipy-dbg"
@@ -171,13 +167,17 @@ install:
 
       if [ "$CPP" = "-std=c++17" ]; then export CPP="-std=c++1z"; fi
     fi
-  elif [ -z "$PYPY" ]; then
-    pip install numpy scipy pytest
+  else
+    export NPY_NUM_BUILD_JOBS=2
+    echo "Installing pytest, numpy, scipy..."
+    ${PYPY:+travis_wait 30} $PY_CMD -m pip install --user --upgrade --quiet pytest numpy scipy
+    echo "done."
 
-    wget -q -O eigen.tar.gz https://bitbucket.org/eigen/eigen/get/3.3.0.tar.gz
+    wget -q -O eigen.tar.gz https://bitbucket.org/eigen/eigen/get/3.3.3.tar.gz
     tar xzf eigen.tar.gz
-    export CMAKE_EXTRA_ARGS="${CMAKE_EXTRA_ARGS} -DCMAKE_INCLUDE_PATH=$PWD/eigen-eigen-26667be4f70b"
+    export CMAKE_EXTRA_ARGS="${CMAKE_EXTRA_ARGS} -DCMAKE_INCLUDE_PATH=$PWD/eigen-eigen-67e894c6cd8f"
   fi
+  set +e
 script:
 - $SCRIPT_RUN_PREFIX cmake ${CMAKE_EXTRA_ARGS}
     -DPYBIND11_PYTHON_VERSION=$PYTHON