cli,http: Use future-compatible --version declaration.

argparse.__init__'s "version" argument is for backward-compatibility with
optparse, and is dropped in python3.

caucase/cli.py

@@ -347,6 +347,10 @@ def main(argv=None):
   """
   parser = argparse.ArgumentParser(
     description='caucase',
+  )
+  parser.add_argument(
+    '--version',
+    action='version',
     version=version.__version__,
   )
   # XXX: currently, it is the server which chooses which digest is used to sign
@@ -635,6 +639,10 @@ def probe(argv=None):
   """
   parser = argparse.ArgumentParser(
     description='caucase probe - Verify basic caucase server functionality',
+  )
+  parser.add_argument(
+    '--version',
+    action='version',
     version=version.__version__,
   )
   parser.add_argument(
@@ -665,6 +673,10 @@ def updater(argv=None, until=utils.until):
   parser = argparse.ArgumentParser(
     description='caucase updater - '
     'Bootstrap certificate and companion files and keep them up-to-date',
+  )
+  parser.add_argument(
+    '--version',
+    action='version',
     version=version.__version__,
   )
   parser.add_argument(
@@ -883,6 +895,10 @@ def rerequest(argv=None):
     description='caucase rerequest - '
     'Produce a new private key and sign a CSR created by copying an existing, '
     'well-signed CSR.',
+  )
+  parser.add_argument(
+    '--version',
+    action='version',
     version=version.__version__,
   )
   parser.add_argument(
@@ -942,6 +958,10 @@ def key_id(argv=None):
     description='caucase key id - '
     'Displays key identifier from private key, and the list of acceptable key'
     'identifiers for a given backup file.',
+  )
+  parser.add_argument(
+    '--version',
+    action='version',
     version=version.__version__,
   )
   parser.add_argument(

caucase/http.py

@@ -416,6 +416,10 @@ def main(
   """
   parser = argparse.ArgumentParser(
     description='caucased',
+  )
+  parser.add_argument(
+    '--version',
+    action='version',
     version=version.__version__,
   )
   parser.add_argument(
@@ -879,6 +883,10 @@ def manage(argv=None):
   """
   parser = argparse.ArgumentParser(
     description='caucased caucased database management tool',
+  )
+  parser.add_argument(
+    '--version',
+    action='version',
     version=version.__version__,
   )
   parser.add_argument(