tox: Add dependency checking environment, do not install dependencies

Signed-off-by: Vasilis Tsiligiannis <acinonyx@openwrt.gr>

.gitlab-ci.yml

@@ -46,6 +46,7 @@ test:
   before_script:
     - pip install tox
   script:
+    - tox -e deps
     - tox -e pytest
 docker:
   stage: deploy

tox.ini

@@ -13,7 +13,16 @@ commands = flake8 \
     setup.py \
     db
 
+[testenv:deps]
+install_command = python -m pip install --no-deps {opts} {packages}
+recreate = True
+deps =
+    -rrequirements-dev.txt
+extras = dev
+commands = pip check
+
 [testenv:pytest]
+install_command = python -m pip install --no-deps {opts} {packages}
 deps =
     -rrequirements-dev.txt
 usedevelop = True