Document issue with gzip and bzip on older pythons

Updates the barman-cloud-wal-archive man page and the argument
help strings to warn people that compression options should not be
used with older python versions (<3.2 for gzip, 3.3 for bzip2).

See issue #325 for the full context.

barman/clients/cloud_walarchive.py

@@ -155,15 +155,17 @@ def parse_arguments(args=None):
     compression.add_argument(
         "-z",
         "--gzip",
-        help="gzip-compress the WAL while uploading to the cloud",
+        help="gzip-compress the WAL while uploading to the cloud "
+        "(should not be used with python < 3.2)",
         action="store_const",
         const="gzip",
         dest="compression",
     )
     compression.add_argument(
         "-j",
         "--bzip2",
-        help="bzip2-compress the WAL while uploading to the cloud",
+        help="bzip2-compress the WAL while uploading to the cloud "
+        "(should not be used with python < 3.3)",
         action="store_const",
         const="bzip2",
         dest="compression",

doc/barman-cloud-wal-archive.1

@@ -16,6 +16,12 @@ This script can be used in the \f[C]archive_command\f[] of a PostgreSQL
 server to ship WAL files to the Cloud.
 Currently AWS S3 and Azure Blob Storage are supported.
 .PP
+Note: If you are running python 2 or older unsupported versions of
+python 3 then avoid the compression options \f[C]--gzip\f[R] or
+\f[C]--bzip2\f[R] as barman-cloud-wal-restore is unable to restore
+gzip-compressed WALs on python < 3.2 or bzip2-compressed WALs on python
+< 3.3.
+.PP
 This script and Barman are administration tools for disaster recovery of
 PostgreSQL servers written in Python and maintained by EnterpriseDB.
 .SH POSITIONAL ARGUMENTS
@@ -64,14 +70,12 @@ test connectivity to the cloud destination and exit
 .RE
 .TP
 .B \-z, \[en]gzip
-gzip\-compress the WAL while uploading to the cloud
-.RS
-.RE
+gzip-compress the WAL while uploading to the cloud (should not be used
+with python < 3.2)
 .TP
 .B \-j, \[en]bzip2
-bzip2\-compress the WAL while uploading to the cloud
-.RS
-.RE
+bzip2-compress the WAL while uploading to the cloud (should not be used
+with python < 3.3)
 .TP
 .B \[en]cloud\-provider {aws\-s3,azure\-blob\-storage}
 the cloud provider to which the backup should be uploaded

doc/barman-cloud-wal-archive.1.md

@@ -18,6 +18,11 @@ This script can be used in the `archive_command` of a PostgreSQL
 server to ship WAL files to the Cloud. Currently AWS S3 and Azure Blob
 Storage are supported.
 
+Note: If you are running python 2 or older unsupported versions of
+python 3 then avoid the compression options `--gzip` or `--bzip2` as
+barman-cloud-wal-restore is unable to restore gzip-compressed WALs
+on python < 3.2 or bzip2-compressed WALs on python < 3.3.
+
 This script and Barman are administration tools for disaster recovery
 of PostgreSQL servers written in Python and maintained by EnterpriseDB.
 
@@ -55,9 +60,11 @@ WAL_PATH
 
 -z, --gzip
 :    gzip-compress the WAL while uploading to the cloud
+     (should not be used with python < 3.2)
 
 -j, --bzip2
 :    bzip2-compress the WAL while uploading to the cloud
+     (should not be used with python < 3.3)
 
 --cloud-provider {aws-s3,azure-blob-storage}
 :    the cloud provider to which the backup should be uploaded