Fix inplace tests

Author: isuruf

bin/test_travis.sh

@@ -10,13 +10,12 @@ mkdir dist-extract
 cd dist-extract
 tar -xvf ../dist/symengine-*.tar.gz
 cd symengine-*
-export PYTHON_SOURCE_DIR=$PWD
 
 # Build inplace so that nosetests can be run inside source directory
 python3 setup.py install build_ext --inplace --symengine-dir=$our_install_dir
 
 # Test python wrappers
 python3 -m pip install pytest
-python3 -m pytest -s -v $PYTHON_SOURCE_DIR/symengine/tests/test_*.py
+python3 -m pytest -s -v $PWD/symengine/tests/test_*.py
 mkdir -p empty && cd empty
 python3 $PYTHON_SOURCE_DIR/bin/test_python.py