fix building error when installing epg2xml with old pip versions

ERROR: Could not find a version that satisfies the requirement epg2xml (unavailable) (from versions: none)
ERROR: No matching distribution found for epg2xml (unavailable)

Dockerfile.ubuntu

@@ -29,9 +29,10 @@ RUN \
         python3 \
         python3-bs4 \
         python3-lxml \
-		python3-pip \
+        python3-pip \
         python3-requests \
         xml-twig-tools && \
+    python3 -m pip install -U pip && \
     echo "**** install epg2xml ****" && \
     EPG2XML_VER=$(wget --no-check-certificate -O - -o /dev/null "https://api.github.com/repos/epg2xml/epg2xml/releases/latest" | awk '/tag_name/{print $4;exit}' FS='[""]') && \
     python3 -m pip install "epg2xml[lxml] @ git+https://github.com/epg2xml/epg2xml.git@${EPG2XML_VER}" && \