enable S3 in travis python builds

ci/travis_script_python.sh

@@ -100,6 +100,10 @@ CMAKE_COMMON_FLAGS="-DARROW_EXTRA_ERROR_CONTEXT=ON"
 
 PYTHON_CPP_BUILD_TARGETS="arrow_python-all plasma parquet"
 
+if [ "$ARROW_TRAVIS_S3" == "1" ]; then
+  CMAKE_COMMON_FLAGS="$CMAKE_COMMON_FLAGS -DARROW_S3=ON"
+fi
+
 if [ "$ARROW_TRAVIS_FLIGHT" == "1" ]; then
   CMAKE_COMMON_FLAGS="$CMAKE_COMMON_FLAGS -DARROW_FLIGHT=ON"
 fi

python/pyarrow/_fs.pyx

@@ -41,7 +41,8 @@ cdef class FileStats:
     """FileSystem entry stats"""
 
     def __init__(self):
-        raise TypeError('dont initialize me')
+        raise TypeError("FileStats cannot be instantiated directly, use "
+                        "FileSystem.get_target_stats method instead.")
 
     @staticmethod
     cdef FileStats wrap(CFileStats stats):

python/pyarrow/tests/conftest.py

@@ -243,18 +243,15 @@ def minio_server():
         'MINIO_SECRET_KEY': secret_key
     })
 
-    minio_dir = os.environ.get('S3FS_DIR', '')
-    minio_bin = os.path.join(minio_dir, 'minio') if minio_dir else 'minio'
-
     try:
         with tempfile.TemporaryDirectory() as tempdir:
-            args = [minio_bin, '--compat', 'server', '--quiet', '--address',
+            args = ['minio', '--compat', 'server', '--quiet', '--address',
                     address, tempdir]
             with subprocess.Popen(args, env=env) as proc:
                 yield address, access_key, secret_key
                 proc.terminate()
     except IOError:
-        pytest.skip('`minio` command cannot be located, try to set S3FS_DIR')
+        pytest.skip('`minio` command cannot be located')
 
 
 @pytest.fixture(scope='module')