Travis: use codecov-bash

Faster to install and will retry uploads on connection errors.

.travis.yml

@@ -94,11 +94,11 @@ after_success:
   - |
     if [[ "$PYTEST_NO_COVERAGE" != 1 ]]; then
       set -e
-      pip install codecov
+      pip install coverage
       coverage combine
       coverage xml --ignore-errors
       coverage report -m --ignore-errors
-      codecov --required -X gcov pycov search -f coverage.xml --flags ${TOXENV//-/ } linux
+      bash <(curl -s https://codecov.io/bash) -Z -X gcov -X coveragepy -X search -X xcode -X gcovout -X fix -f coverage.xml -F "${TOXENV//-/,},linux"
 
       # Coveralls does not support merged reports.
       if [[ "$TOXENV" = py37 ]]; then