Update docker images

.github/ci_images/f31_builder.dockerfile

@@ -1,7 +1,7 @@
-FROM fedora:30
+FROM fedora:31
 
 ENV LANG C.UTF-8
-ENV OS_NAME f30
+ENV OS_NAME f31
 
 RUN dnf install -y --nodocs \
 # Base build tools
@@ -11,6 +11,8 @@ RUN dnf install -y --nodocs \
     mingw32-gcc-c++ mingw32-bzip2-static mingw32-win-iconv-static \
     mingw32-winpthreads-static mingw32-zlib-static mingw32-xz-libs-static \
     mingw32-libmicrohttpd \
+# python3
+    python-unversioned-command \
 # Other tools (to remove)
 #    vim less grep
   && dnf remove -y "*-doc" \

.github/ci_images/xenial_builder.dockerfile

@@ -9,7 +9,7 @@ RUN apt update -q \
 # Base build tools
     build-essential automake libtool cmake ccache pkg-config autopoint patch \
     python3-pip python3-setuptools python3-wheel git subversion wget unzip \
-    ninja-build openssh-client \
+    ninja-build openssh-client curl \
 # Python (2) is needed to install android-ndk
     python \
 # Packaged dependencies

.github/workflows/base.yml

@@ -3,14 +3,14 @@ name: Build Base
 on: [push]
 
 env:
-  DOCKER_VERSION: 25
+  DOCKER_VERSION: 26
 
 jobs:
   Docker:
     strategy:
       fail-fast: false
       matrix:
-        variant: [xenial, bionic, f30, focal]
+        variant: [xenial, bionic, f31, focal]
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
@@ -65,10 +65,10 @@ jobs:
             image_variant: xenial
             lib_postfix: '/x86_64-linux-gnu'
           - target: win32_static
-            image_variant: f30
+            image_variant: f31
             lib_postfix: '64'
           - target: win32_dyn
-            image_variant: f30
+            image_variant: f31
             lib_postfix: '64'
           - target: i586_static
             image_variant: xenial
@@ -94,7 +94,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: Docker
     container:
-      image: "kiwix/kiwix-build_ci:${{matrix.image_variant}}-25"
+      image: "kiwix/kiwix-build_ci:${{matrix.image_variant}}-26"
     steps:
     - name: Checkout code
       shell: bash