Skip tests if deepforest not present instead of skipping on CRAN

This lets tests run on CI and follows recommend practice:
https://rstudio.github.io/reticulate/articles/package.html#checking-and-testing-on-cran

tests/testthat/test-integration.R

@@ -2,47 +2,33 @@ library(testthat)
 
 context("integration tests for DeepForest in R")
 
-test_that("deepforest model is installed", {
-    
-    # Python package not installed on CRAN
-
-    skip_on_cran() 
+skip_if_no_deepforest <- function() {
+  deepforest_avail <- py_module_available("deepforest")
+  if (!deepforest)
+    skip("deepforest not available for testing")
+}
 
+test_that("deepforest model is installed", {
+  skip_if_no_deepforest()
   deepforest_available = reticulate::py_module_available("deepforest")
   expect_identical(deepforest_available, TRUE)
 })
 
 test_that("deepforest model exists when loaded", {
-
-  # Python package not installed on CRAN
-
-    skip_on_cran() 
-
+  skip_if_no_deepforest()
   model = df_model()
   expect_type(model, "closure")
-
 })
 
 test_that("use_release model exists when loaded", {
-
-  # Python package not installed on CRAN
-
-    skip_on_cran() 
-
+  skip_if_no_deepforest()
   model = df_model()
   model$use_release()
   expect_type(model, "closure")
-
 })
 
 test_that("image prediction works", {
-
-  # Python package not installed on CRAN
-
-    skip_on_cran() 
-
-  expect
-
+  skip_if_no_deepforest()
   model = df_model()
   model$use_release()
   image_path = get_data("OSBS_029.png")
@@ -51,9 +37,7 @@ test_that("image prediction works", {
 })
 
 test_that("training works", {
-
-  skip_on_cran()
-
+  skip_if_no_deepforest()
   model = df_model()
   model$use_release()
   annotations_file = get_data("testfile_deepforest.csv")
@@ -65,4 +49,4 @@ test_that("training works", {
   model$create_trainer()
   model$trainer$fit(model)
   expect_type(model, "closure")
-})
+})