Add PiWheels support

Dockerfile

@@ -3,11 +3,24 @@ FROM python:3
 # Set working space
 WORKDIR /usr/src/app
 
-# Install requirements
-RUN ln -snf /usr/share/zoneinfo/Europe/Rome /etc/localtime && \
-    apt-get update && apt-get install -y wkhtmltopdf
+# Install dependencies
+RUN apt-get update \
+    # Prevent endless waiting
+    && DEBIAN_FRONTEND=noninteractive \
+    # Set UTC as timezone
+    && ln -snf /usr/share/zoneinfo/Europe/Rome /etc/localtime \
+    # Install APT packages
+    && apt-get install -y --fix-missing wkhtmltopdf \
+    # Remove tmp files
+    && apt-get clean && rm -rf /tmp/* /var/tmp/* \
+    # Add PiWheels support
+    && echo "[global]\nextra-index-url=https://www.piwheels.org/simple" >> /etc/pip.conf \
+    # Upgrade PIP 
+    && python3 -m pip install --no-cache-dir --upgrade pip
+
+# Copy and install requirements
 COPY requirements.txt .
-RUN pip install -r requirements.txt
+RUN python3 -m pip install -r requirements.txt
 
 # Copy app
 COPY . .
@@ -16,4 +29,4 @@ COPY . .
 RUN mkdir out
 
 # Start the bot
-CMD python -u bot.py
+CMD python3 -u bot.py