Better error messages from python-jl

src/julia/python_jl.jl

@@ -0,0 +1,49 @@
+if VERSION < v"0.7-"
+    error("Unsupported Julia version: $VERSION")
+end
+
+import PyCall
+
+@debug "Trying to import Python module `julia`..."
+try
+    PyCall.pyimport("julia")
+catch err
+    if PyCall.pyisinstance(err.val, PyCall.pybuiltin("ImportError"))
+        @error """
+Python module `julia` cannot be imported.  It is likely that you are
+installing PyJulia in the Python environment that is not used by PyCall.  Note
+that `python-jl` program needs PyJulia to be installed in the Python environment
+used by PyCall.
+
+PyCall is configured to use Python executable:
+    $(PyCall.pyprogramname)
+
+See PyCall documentation:
+    https://github.com/JuliaPy/PyCall.jl#specifying-the-python-version
+        """
+        exit(1)
+    end
+    rethrow()
+end
+
+@debug "Trying to import Python module `julia.pseudo_python_cli`..."
+let cli = try
+        PyCall.pyimport("julia.pseudo_python_cli")
+    catch err
+        if PyCall.pyisinstance(err.val, PyCall.pybuiltin("ImportError"))
+            @error "Incompatible version of PyJulia is installed for PyCall."
+            exit(1)
+        end
+        rethrow()
+    end,
+    main = try
+        cli.main
+    catch
+        cli[:main]
+    end,
+    code = main(ARGS)
+
+    if code isa Integer
+        exit(code)
+    end
+end

src/julia/python_jl.py

@@ -21,6 +21,7 @@
 
 from __future__ import absolute_import, print_function
 
+import os
 import sys
 
 from .pseudo_python_cli import ARGUMENT_HELP, make_parser, parse_args_with
@@ -33,15 +34,7 @@
 """
 )
 
-script_jl = """
-import PyCall
-
-let code = PyCall.pyimport("julia.pseudo_python_cli")[:main](ARGS)
-    if code isa Integer
-        exit(code)
-    end
-end
-"""
+script_jl = os.path.join(os.path.dirname(os.path.realpath(__file__)), "python_jl.jl")
 
 
 def remove_julia_options(args):
@@ -111,7 +104,7 @@ def main(args=None):
         args = sys.argv[1:]
     ns, unused_args = parse_pyjl_args(args)
     julia = ns.julia
-    execprog([julia, "-e", script_jl, "--"] + unused_args)
+    execprog([julia, script_jl, "--"] + unused_args)
 
 
 if __name__ == "__main__":