Fix: detect IPython and require magic for imports

On IPython, the kernel adds $PWD to sys.path before proceeding
to import lots of modules. In order to remove the restriction
that user submodule notebook names not shadow existing libraries
we can remove $PWD from the sys.path under IPython.
Once the kernel has started, experienced users *might* expect $PWD
to be on sys.path. Literary only restores this for non-__package__
notebooks.  This would also work out-of-the-box for top-level
notebooks, but not inside e.g. examples/ folders.

examples/absolute-importing.ipynb

@@ -21,18 +21,6 @@
     "We are going to use the _notebook_ hook, which adds support for importing other notebooks. This is different to the _module_ hook, which can be seen in [src/package_a/importer.ipynb](src/package_a/importer.ipynb)"
    ]
   },
-  {
-   "cell_type": "code",
-   "execution_count": 1,
-   "id": "satisfactory-discretion",
-   "metadata": {
-    "tags": []
-   },
-   "outputs": [],
-   "source": [
-    "%load_ext literary.notebook"
-   ]
-  },
   {
    "cell_type": "markdown",
    "id": "favorite-questionnaire",
@@ -187,7 +175,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.4"
+   "version": "3.10.4"
   }
  },
  "nbformat": 4,

examples/src/package_a/__init__.ipynb

@@ -25,7 +25,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.4"
+   "version": "3.10.4"
   }
  },
  "nbformat": 4,

examples/src/package_a/docstring.ipynb

@@ -24,7 +24,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -38,7 +38,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.0"
+   "version": "3.10.4"
   }
  },
  "nbformat": 4,

examples/src/package_a/exports.ipynb

@@ -96,7 +96,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.4"
+   "version": "3.10.4"
   }
  },
  "nbformat": 4,

examples/src/package_a/importer.ipynb

@@ -23,38 +23,6 @@
     "## Loaded modules"
    ]
   },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "### Loading the hook"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "First we need to run the shim that installs the import hook and loads the useful globals:"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 1,
-   "metadata": {
-    "tags": []
-   },
-   "outputs": [],
-   "source": [
-    "%load_ext literary.module"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "This is **only needed if we wish to execute this notebook directly**, as the import hook performs this step automatically when importing notebooks. Defining `__package__` enables us to perform relative imports. Let's import a function from [exports.ipynb]():"
-   ]
-  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -408,7 +376,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.4"
+   "version": "3.10.4"
   }
  },
  "nbformat": 4,

examples/src/package_a/patching.ipynb

@@ -226,29 +226,6 @@
     "## `@patch` decorator"
    ]
   },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "The `%load_ext literary.module` magic can be used to load a `patch` decorator from Literary:"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 9,
-   "metadata": {
-    "execution": {
-     "iopub.execute_input": "2021-05-18T21:00:06.297765Z",
-     "iopub.status.busy": "2021-05-18T21:00:06.297160Z",
-     "iopub.status.idle": "2021-05-18T21:00:06.442965Z",
-     "shell.execute_reply": "2021-05-18T21:00:06.441843Z"
-    }
-   },
-   "outputs": [],
-   "source": [
-    "%load_ext literary.module"
-   ]
-  },
   {
    "cell_type": "code",
    "execution_count": 10,
@@ -376,7 +353,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -390,7 +367,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.0"
+   "version": "3.10.4"
   }
  },
  "nbformat": 4,