Travis: Install Python 3 to run Python 3 tests.

Install Python 3.3 from the Deadsnakes PPA. As this doesn't have pip,
install it manually into ~/.local.

~/.local/bin is apparently in Travis's default PATH, meaning "pip"
doesn't refer to Python 2's pip anymore, but to the manually
installed Python 3 version. Updated the scripts to use version-
suffixed executable names (e.g. pip2.7).

Set CC=cc to use system's default compiler when installing Python
modules, as gcc on OS X had a problem with compiling one of the
dependencies of the Neovim Python module.

.ci/before_install.sh

@@ -10,4 +10,19 @@ fi
 if [[ "${TRAVIS_OS_NAME}" == osx ]]; then
   brew update
 fi
-pip install --user --upgrade pip
+
+echo "Upgrade Python 2's pip."
+pip2.7 install --user --upgrade pip
+
+if [[ "${TRAVIS_OS_NAME}" == osx ]]; then
+  echo "Install Python 3."
+  brew install python3
+  echo "Upgrade Python 3's pip."
+  pip3 install --user --upgrade pip
+else
+  # TODO: Replace with upgrade when Travis gets python3-pip package.
+  echo "Install pip for Python 3."
+  curl -sSL https://bootstrap.pypa.io/get-pip.py -o "${HOME}/get-pip.py"
+  # After this, pip in PATH will refer to Python 3's pip.
+  python3.3 "${HOME}/get-pip.py" --user --upgrade
+fi

.ci/install.sh

@@ -14,7 +14,17 @@ elif [[ "${BUILD_MINGW}" == ON ]]; then
   # binutils-mingw-w64-i686 gcc-mingw-w64-i686 g++-mingw-w64-i686 mingw-w64-dev mingw-w64-tools
 
   echo "Downloading MinGW..."
-  wget -q -O - "http://downloads.sourceforge.net/project/mingw-w64/Toolchains%20targetting%20Win32/Personal%20Builds/rubenvb/gcc-4.8-release/i686-w64-mingw32-gcc-4.8.0-linux64_rubenvb.tar.xz" | tar xJf - -C "${HOME}/.local"
+  curl -sSL "http://downloads.sourceforge.net/project/mingw-w64/Toolchains%20targetting%20Win32/Personal%20Builds/rubenvb/gcc-4.8-release/i686-w64-mingw32-gcc-4.8.0-linux64_rubenvb.tar.xz" | tar xJf - -C "${HOME}/.local"
 fi
 
-pip install --user --upgrade cpp-coveralls neovim
+# Set CC to default to avoid compilation problems
+# when installing Python modules.
+echo "Install neovim module and coveralls for Python 2."
+CC=cc pip2.7 install --user --upgrade neovim cpp-coveralls
+
+echo "Install neovim module for Python 3."
+if [[ "${TRAVIS_OS_NAME}" == osx ]]; then
+  CC=cc pip3 install --user --upgrade neovim
+else
+  CC=cc pip3.3 install --user --upgrade neovim
+fi

.travis.yml

@@ -9,7 +9,7 @@ env:
     # http://docs.travis-ci.com/user/speeding-up-the-build/#Paralellizing-your-build-on-one-VM
     - MAKE_CMD="make -j2"
     # Update PATH for pip and MinGW.
-    - PATH="$(python -c 'import site; print(site.getuserbase())')/bin:$HOME/.local/mingw32/bin:$PATH"
+    - PATH="$(python2.7 -c 'import site; print(site.getuserbase())')/bin:$HOME/.local/mingw32/bin:$PATH"
     # LLVM symbolizer path.
     - LLVM_SYMBOLIZER="$(which llvm-symbolizer-3.6)"
     # Force verification of DLOG macros.
@@ -101,28 +101,29 @@ after_success:  .ci/after_success.sh
 addons:
   apt:
     sources:
+      # TODO: Remove PPA when Travis gets Python >=3.3.
+      - deadsnakes
       - llvm-toolchain-precise-3.6
       - ubuntu-toolchain-r-test
     packages:
-      # Basic Neovim/test dependencies.
       - autoconf
       - automake
       - build-essential
-      - cmake
-      - gdb
-      - libtool
-      - pkg-config
-      - unzip
-      - xclip
-      # Additional compilers/tools.
       - clang-3.6
+      - cmake
       - g++-5-multilib
       - g++-multilib
       - gcc-5-multilib
       - gcc-multilib
+      - gdb
       - libc6-dev-i386
+      - libtool
       - llvm-3.6-dev
+      - pkg-config
+      - python3.3-dev
+      - unzip
       - valgrind
+      - xclip
 
 branches:
   except: