Include python3 in travis

Author: schedutron

.travis.yml

@@ -7,6 +7,7 @@ matrix:
         - os: osx
           osx_image: xcode8.3
           compiler: clang
+          python: 3.6
           env:
               # NAME has no actual use, just to make the travis jobs overview more clear
               - NAME="clang Debug"
@@ -25,6 +26,7 @@ matrix:
                       - ubuntu-toolchain-r-test
                   packages:
                     - g++-4.8
+          python: 3.6
           env:
               # NAME has no actual use, just to make the travis jobs overview more clear
               - NAME="gcc4.8 Debug+Tests+Coveralls"
@@ -67,6 +69,7 @@ matrix:
                       - ubuntu-toolchain-r-test
                   packages:
                     - g++-4.8
+          python: 3.6
           env:
               # NAME has no actual use, just to make the travis jobs overview more clear
               - NAME="gcc4.8 Release+Tests"
@@ -107,6 +110,7 @@ matrix:
                       - ubuntu-toolchain-r-test
                   packages:
                     - g++-5
+          python: 3.6
           env:
               # NAME has no actual use, just to make the travis jobs overview more clear
               - NAME="gcc5 Debug"
@@ -126,6 +130,7 @@ matrix:
                       - ubuntu-toolchain-r-test
                   packages:
                     - g++-5
+          python: 3.6
           env:
               # NAME has no actual use, just to make the travis jobs overview more clear
               - NAME="gcc5 Release"
@@ -141,7 +146,7 @@ install:
 
 before_script:
     # first, run source_validator
-    - python3 -m script.validators.source_validator
+    - python -m script.validators.source_validator
 
 # build peloton (override this value to execute tests)
 script: