Merge pull request #1634 from ColinFinck/fix-mingw

Fix MinGW bootstrap build.
diff --git a/.travis.yml b/.travis.yml
index e874076..cffa8b3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -31,7 +31,7 @@
   - if [[ "$TRAVIS_OS_NAME" == "windows" ]]; then choco install re2c python ; fi
 script:
   - ./misc/ci.py
-  - ./configure.py --bootstrap
+  - python3 configure.py --bootstrap
   - ./ninja all
   - ./ninja_test --gtest_filter=-SubprocessTest.SetWithLots
   - ./misc/ninja_syntax_test.py