Update the Swift 5.4 Dockerfiles to use python3

Author: shahmishal

5.4/centos/7/Dockerfile

@@ -13,7 +13,7 @@ RUN yum install shadow-utils.x86_64 -y \
   libicu-devel \
   libstdc++-static \
   pkg-config \
-  python2 \
+  python3 \
   sqlite \
   zlib-devel
 

5.4/centos/8/Dockerfile

@@ -15,11 +15,11 @@ RUN yum install --enablerepo=powertools -y \
   libicu-devel \
   libstdc++-static \
   pkg-config \
-  python2 \
+  python3 \
   sqlite \
   zlib-devel
 
-RUN ln -s /usr/bin/python2 /usr/bin/python
+RUN ln -s /usr/bin/python3 /usr/bin/python
 
 # Everything up to here should cache nicely between Swift versions, assuming dev dependencies change little
 

5.4/ubuntu/16.04/Dockerfile

@@ -14,7 +14,7 @@ RUN export DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true && ap
     libgcc-5-dev \
     libstdc++-5-dev \
     zlib1g-dev \
-    libpython2.7 \
+    libpython3.5 \
     tzdata \
     git \
     pkg-config \

5.4/ubuntu/18.04/Dockerfile

@@ -14,7 +14,7 @@ RUN export DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true && ap
     libgcc-5-dev \
     libstdc++-5-dev \
     zlib1g-dev \
-    libpython2.7 \
+    libpython3.6 \
     tzdata \
     git \
     pkg-config \

5.4/ubuntu/20.04/Dockerfile

@@ -11,7 +11,7 @@ RUN export DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true && ap
     libcurl4 \
     libedit2 \
     libgcc-9-dev \
-    libpython2.7 \
+    libpython3.8 \
     libsqlite3-0 \
     libstdc++-9-dev \
     libxml2 \