configure.ac: disable pytz with --disable-doc and --disable-r

The pytz package is a dependency of three others: babel, rpy2, and
tzlocal. And tzlocal is itself a dependency of rpy2. Babel is already
disabled with --disable-doc, and rpy2 and tzlocal are disabled with
--disable-r. It therefore makes sense to disable pytz when both
--disable-doc and --disable-r are given.

Author: orlitzky

configure.ac

@@ -512,12 +512,6 @@ AC_ARG_ENABLE([notebook],
     done
   ])
 
-AS_IF([test "$SAGE_ENABLE_notebook" = no -a "$SAGE_ENABLE_sagelib" = no], [
-    for pkg in jupyter_client ipykernel ipython zeromq pyzmq; do
-      AS_VAR_SET([SAGE_ENABLE_$pkg], [$enableval])
-    done
-  ])
-
 AC_ARG_ENABLE([r],
   AS_HELP_STRING([--disable-r],
                  [disable build of the R package and related packages]), [
@@ -546,6 +540,22 @@ AC_ARG_ENABLE([sagelib],
     done
   ])
 
+
+dnl Handle combinations of --disable-foo flags that may enable us to
+dnl prune even more dependencies.
+AS_IF([test "$SAGE_ENABLE_notebook" = no -a "$SAGE_ENABLE_sagelib" = no], [
+    for pkg in jupyter_client ipykernel ipython zeromq pyzmq; do
+      AS_VAR_SET([SAGE_ENABLE_$pkg], [$enableval])
+    done
+  ])
+AS_IF([test "$SAGE_ENABLE_r" = no -a "$SAGE_ENABLE_sage_docbuild" = no], [
+  dnl pytz is needed only by rpy2 and babel, and babel is already
+  dnl disabled by --disable-doc.
+  for pkg in pytz; do
+    AS_VAR_SET([SAGE_ENABLE_$pkg], [$enableval])
+  done
+])
+
 dnl Packages that require a special override to use the SPKG
 dnl when the system package is not usable.
 AS_VAR_SET([sage_use_system_gcc], [force])