one more attempt to fix Docker builds

they are failing because pycparser has issues with --no-cache-dir
solution picked from pypa/pip#6158 (comment)

Dockerfile

@@ -7,9 +7,10 @@ ENV PYTHONPATH $PYTHONPATH:/app
 COPY requirements.txt /app/requirements.txt
 
 RUN apk --update add gcc git musl-dev libxml2-dev libxslt-dev libffi-dev openssl-dev \
-        && pip install --upgrade setuptools pip \
-        && pip install --no-cache-dir --requirement /app/requirements.txt \
-        && pip install --no-cache-dir Scrapy==0.24.6 \
+        && pip install --cache-dir=/tmp/pipcache --upgrade setuptools pip \
+        && pip install --cache-dir=/tmp/pipcache --requirement /app/requirements.txt \
+        && pip install --cache-dir=/tmp/pipcache Scrapy==0.24.6 \
+        && rm -r /tmp/pipcache \
         && apk del gcc git musl-dev \
         && rm /var/cache/apk/*
 

hyphe_backend/crawler/Dockerfile

@@ -3,12 +3,13 @@ FROM python:2.7-alpine
 COPY requirements-global-scrapyd.txt /requirements-global-scrapyd.txt
 
 RUN apk --update add gcc musl-dev libffi-dev openssl-dev libxml2-dev libxslt-dev \
-        && pip install --upgrade setuptools pip \
-        && pip install --no-use-pep517 --no-cache-dir -r requirements-global-scrapyd.txt \
-        && pip install --no-cache-dir Scrapy==0.24.6 \
-        && pip install --no-cache-dir scrapyd==1.0.1 \
+        && pip install --cache-dir=/tmp/pipcache --upgrade setuptools pip \
+        && pip install --cache-dir=/tmp/pipcache -r requirements-global-scrapyd.txt \
+        && pip install --cache-dir=/tmp/pipcache Scrapy==0.24.6 \
+        && pip install --cache-dir=/tmp/pipcache scrapyd==1.0.1 \
+        && rm -r /tmp/pipcache \
         && apk del gcc musl-dev \
-	&& rm /var/cache/apk/*
+        && rm /var/cache/apk/*
 
 COPY scrapyd.config /etc/scrapyd/conf.d/100-hyphe