diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index bdb2c7f4206e55a535eaf638272f2feca4d33bf8..52cb3b2a0b779f97f4fa7b838b38a91d95df874a 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,6 +1,6 @@
 # Official language image. Look for the different tagged releases at:
 # https://hub.docker.com/r/library/python/tags/
-image: ${CI_DEPENDENCY_PROXY_DIRECT_GROUP_IMAGE_PREFIX}/python:3.6
+image: ${CI_DEPENDENCY_PROXY_DIRECT_GROUP_IMAGE_PREFIX}/python:latest
 
 # Change pip's cache directory to be inside the project directory since we can
 # only cache local items.
@@ -41,6 +41,42 @@ unit-test-job:
     reports:
       junit: nose2-junit.xml
 
+unit-test-2.7-job:
+  image: ${CI_DEPENDENCY_PROXY_DIRECT_GROUP_IMAGE_PREFIX}/python:2.7
+  stage: test
+  script:
+    - make test
+
+unit-test-3.7-job:
+  image: ${CI_DEPENDENCY_PROXY_DIRECT_GROUP_IMAGE_PREFIX}/python:3.7
+  stage: test
+  script:
+    - make test 2>&1 | tee errors-3.7.log
+  artifacts:
+    when: always
+    paths:
+      - errors-3.7.log
+
+unit-test-3.8-job:
+  image: ${CI_DEPENDENCY_PROXY_DIRECT_GROUP_IMAGE_PREFIX}/python:3.8
+  stage: test
+  script:
+    - make test 2>&1 | tee errors-3.8.log
+  artifacts:
+    when: always
+    paths:
+      - errors-3.8.log
+
+unit-test-3.9-job:
+  image: ${CI_DEPENDENCY_PROXY_DIRECT_GROUP_IMAGE_PREFIX}/python:3.9
+  stage: test
+  script:
+    - make test 2>&1 | tee errors-3.9.log
+  artifacts:
+    when: always
+    paths:
+      - errors-3.9.log
+
 pylint-test-job:
   stage: test
   script:
@@ -58,6 +94,27 @@ check-deprecation-warnings:
     - "if [[ $(grep DeprecationWarning errors.log) ]]; then cat errors.log; exit 1; fi"
   allow_failure: true
 
+check-deprecation-warnings-3.7:
+  before_script: []
+  stage: check-warnings
+  script:
+    - "if [[ $(grep DeprecationWarning errors-3.7.log) ]]; then cat errors-3.7.log; exit 1; fi"
+  allow_failure: true
+
+check-deprecation-warnings-3.8:
+  before_script: []
+  stage: check-warnings
+  script:
+    - "if [[ $(grep DeprecationWarning errors-3.8.log) ]]; then cat errors-3.8.log; exit 1; fi"
+  allow_failure: true
+
+check-deprecation-warnings-3.9:
+  before_script: []
+  stage: check-warnings
+  script:
+    - "if [[ $(grep DeprecationWarning errors-3.9.log) ]]; then cat errors-3.9.log; exit 1; fi"
+  allow_failure: true
+
 build-job:
   stage: build
   script:
diff --git a/Makefile b/Makefile
index f1966d4b216840d4d862b08b428d925494316114..d248c5ef0ba7e5d67a5475368c1556d55648a307 100644
--- a/Makefile
+++ b/Makefile
@@ -98,7 +98,7 @@ help:
 
 
 show-version: FORCE
-	@PYTHONPATH=lib python3 -c "import ipranges; print(ipranges.__version__);"
+	@PYTHONPATH=lib python -c "import ipranges; print(ipranges.__version__);"
 
 
 #-------------------------------------------------------------------------------
@@ -108,13 +108,13 @@ deps: deps-python deps-python-dev
 
 deps-python-dev: FORCE
 	@echo "\n$(GREEN)*** Installing Python development dependencies ***$(NC)\n"
-	@pip3 --version
-	@pip3 install -r requirements-dev.pip
+	@pip --version
+	@pip install -r requirements-dev.pip
 
 deps-python: FORCE
 	@echo "\n${GREEN}*** Installing Python dependencies ***${NC}\n"
 	@echo "\nThis project does not have any dependencies, nothing to do here...\n"
-	@#pip3 install -r requirements.pip --upgrade
+	@#pip install -r requirements.pip --upgrade
 
 
 #-------------------------------------------------------------------------------
@@ -138,11 +138,11 @@ pyflakes:
 
 pyflakes-lib: FORCE
 	@echo "\n${GREEN}*** Checking code with pyflakes ***${NC}\n"
-	-@python3 -m pyflakes ipranges.py
+	-@python -m pyflakes ipranges.py
 
 pyflakes-test: FORCE
 	@echo "\n${GREEN}*** Checking test files with pyflakes ***${NC}\n"
-	-@python3 -m pyflakes test_ipranges.py
+	-@python -m pyflakes test_ipranges.py
 
 #pylint: pylint-lib pylint-test
 pylint:
@@ -150,11 +150,11 @@ pylint:
 
 pylint-lib: FORCE
 	@echo "\n${GREEN}*** Checking code with pylint ***${NC}\n"
-	-@python3 -m pylint ipranges.py --rcfile .pylintrc-lib
+	-@python -m pylint ipranges.py --rcfile .pylintrc-lib
 
 pylint-test: FORCE
 	@echo "\n${GREEN}*** Checking test files with pylint ***${NC}\n"
-	-@python3 -m pylint test_ipranges.py --rcfile .pylintrc-test
+	-@python -m pylint test_ipranges.py --rcfile .pylintrc-test
 
 test: FORCE
 	@echo "\n${GREEN}*** Checking code with nosetests ***${NC}\n"
@@ -172,11 +172,11 @@ archive: FORCE
 
 bdist: FORCE
 	@echo "\n${GREEN}*** Building Python packages ***${NC}\n"
-	@python3 setup.py sdist bdist_wheel --universal
+	@python setup.py sdist bdist_wheel --universal
 
 install: FORCE
 	@echo "\n${GREEN}*** Performing local installation ***${NC}\n"
-	@pip3 install dist/ipranges*.whl --upgrade
+	@pip install dist/ipranges*.whl --upgrade
 
 deploy: FORCE
 	@echo "\n${GREEN}*** Deploying packages to PyPI ***${NC}\n"
diff --git a/requirements-dev.pip b/requirements-dev.pip
index 85211981c432378064d8ddd59f612d087a06a2d9..67caa2415dccb8ca41123a036f0e606d547b4c1d 100644
--- a/requirements-dev.pip
+++ b/requirements-dev.pip
@@ -3,7 +3,7 @@ wheel
 twine
 docutils<0.18
 nose2
-pyflakes==2.1.0
-pylint==2.2.2
-sphinx==1.8.4
-sphinx-rtd-theme==0.4.2
+pyflakes
+pylint
+sphinx
+sphinx-rtd-theme