Introduce 'get_pip' macro

We have code for it in four places so it is a good candidate for macro.

Change-Id: Icadcbbe5b386bdf688fd67e8160b40974f047377

docker/crane/Dockerfile.j2

@@ -45,9 +45,7 @@ RUN echo 'crane not yet available for {{ base_distro }}' && /bin/false
     {% endif %}
 
 {% block crane_source_install_python_pip %}
-RUN curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py \
-    && python get-pip.py \
-    && rm get-pip.py
+{{ macros.get_pip() }}
 {% endblock %}
 
 ADD crane-archive /crane-source

docker/helm-repository/Dockerfile.j2

@@ -35,9 +35,7 @@ ENV helm_version=2.3.0 \
 {{ macros.install_packages(helm_repo_packages | customizable("packages")) }}
 
 {% block helm_repository_source_install_python_pip %}
-RUN curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py \
-    && python get-pip.py \
-    && rm get-pip.py
+{{ macros.get_pip() }}
 {% endblock %}
 
 {% set helm_repository_pip_packages = [

docker/kolla-toolbox/Dockerfile.j2

@@ -47,9 +47,7 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
 {{ macros.install_packages(kolla_toolbox_packages | customizable("packages")) }}
 
 {% block kolla_toolbox_source_install_python_pip %}
-RUN curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py \
-    && python get-pip.py \
-    && rm get-pip.py
+{{ macros.get_pip() }}
 {% endblock %}
 
 {% set kolla_toolbox_pip_virtualenv_packages = [

docker/macros.j2

@@ -21,6 +21,12 @@
 {% endif %}
 {%- endmacro %}
 
+{% macro get_pip() %}
+RUN curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py \
+    && python get-pip.py \
+    && rm get-pip.py
+{% endmacro %}
+
 {% macro install_pip(packages, constraints = true, pip_version = pip) %}
 {%- if packages is sequence and packages|length > 0 -%}
 {%- if not pip_version -%}

docker/openstack-base/Dockerfile.j2

@@ -185,9 +185,7 @@ ENV DEBIAN_FRONTEND noninteractive
 {{ macros.install_packages(openstack_base_packages | customizable("packages")) }}
 
 {% block source_install_python_pip %}
-RUN curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py \
-    && python get-pip.py \
-    && rm get-pip.py
+{{ macros.get_pip() }}
 {% endblock %}
 
 {% set openstack_base_pip_packages = [

releasenotes/notes/get_pip-macro-906a78462b216049.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    New macro: 'get_pip' allows to bootstrap 'pip' in image.