Merge branch 'v2.9'

docker/centos7

@@ -2,6 +2,7 @@ FROM centos:7
 
 # NOTE: numpy==1.19 is the last version compatible with python 3.6
 # NOTE: pillow==8.4.0 leads to an error while installing on centos7
+# NOTE: gsd 3 does not compile on centos7
 RUN yum -y update \
  && yum -y group install "Development Tools" \
  && yum -y install environment-modules gawk vim wget \
@@ -10,6 +11,7 @@ RUN yum -y update \
  && pip3 install pillow==8.3.2 \
  && pip3 install numpy==1.19 \
  && pip3 install cython numpy pandas mdtraj \
+ && pip3 install "gsd<3" \
  && pip3 install MDAnalysis==1.0.0
 
 RUN useradd -ms /bin/bash plumed