Add JULIA_BINDDIR environment variable for julia v0.7+

Add tests for the ENVIRONMENT VARIABLES to the julia unit tests.

repo2docker/buildpacks/julia/__init__.py

@@ -71,7 +71,8 @@ class JuliaBuildPack(CondaBuildPack):
         """
         return super().get_build_env() + [
             ('JULIA_PATH', '${APP_BASE}/julia'),
-            ('JULIA_HOME', '${JULIA_PATH}/bin'),
+            ('JULIA_HOME', '${JULIA_PATH}/bin'),  # julia <= 0.6
+            ('JULIA_BINDIR', '${JULIA_HOME}'),  # julia >= 0.7
             ('JULIA_PKGDIR', '${JULIA_PATH}/pkg'),
             ('JULIA_VERSION', self.julia_version),
             ('JUPYTER', '${NB_PYTHON_PREFIX}/bin/jupyter')

tests/julia/julia_version-1/verify

@@ -4,9 +4,12 @@ if VERSION < v"1"
     exit(1)
 end
 
-# Test that the package was installed.
 try
+    # Test that the package was installed.
     using Compat
+
+    # Verify that the environment variables are set correctly for julia 1.0+
+    @assert "julia" ∈ readdir(Sys.BINDIR)
 catch
     exit(1)
 end

tests/julia/julia_version/verify

@@ -4,9 +4,12 @@ if VERSION != v"0.6.3"
     exit(1)
 end
 
-# Test that the package was installed.
 try
+    # Test that the package was installed.
     using Compat
+
+    # Verify that the environment variables are set correctly for julia <= 0.6
+    @assert "julia" ∈ readdir(Base.JULIA_HOME)
 catch
     exit(1)
 end