Merge #1 (add custom inputs).

action.yml

@@ -1,12 +1,22 @@
 name: Install Python dependencies
+description: Install dependencies from a requirements file into a virtualenv.
+inputs:
+  requirements-file:
+    default: "requirements/development.txt"
+    description: Requirements file containing a list of Python packages.
+    required: False
+  virtualenv-location:
+    default: "~/venv"
+    description: Folder where the virtualenv will be located.
+    required: False
 runs:
   using: composite
   steps:
     - name: Create Python virtualenv
       run: |
-        mkdir -p ~/venv
-        python3.7 -m venv ~/venv;
+        mkdir -p ${{ inputs.virtualenv-location }}
+        python3.7 -m venv ${{ inputs.virtualenv-location }};
       shell: bash
     - name: Install requirements
-      run: ~/venv/bin/pip install -r requirements/development.txt
+      run: ${{ inputs.virtualenv-location }}/bin/pip install -r ${{ inputs.requirements-file }}
       shell: bash