python: remove py::implicitly_convertible<py::array> for array views.

This now causes construction of SceneFieldData from a 2D view to do
`import numpy` internally because of some extremely crazy internal
behavior (as shown in the now-deleted comment in the code). Turns out
everything still works even without marking the types implicitly
convertible from py::array (as it should, anyway), so I suspect that was
only needed long time ago for some strange reason, or maybe on some
older and no longer supported pybind11 version.

This reverts commit eb6576c6af.

src/python/corrade/containers.cpp

@@ -24,7 +24,6 @@
 */
 
 #include <pybind11/pybind11.h>
-#include <pybind11/numpy.h> /* so ArrayView is convertible from python array */
 #include <Corrade/Containers/Array.h>
 #include <Corrade/Containers/BitArray.h>
 #include <Corrade/Containers/StridedBitArrayView.h>
@@ -118,8 +117,6 @@ template<class T> void arrayView(py::class_<Containers::ArrayView<T>, Containers
 
     /* Implicitly convertible from a buffer */
     py::implicitly_convertible<py::buffer, Containers::ArrayView<T>>();
-    /* This is needed for implicit conversion from np.array */
-    py::implicitly_convertible<py::array, Containers::ArrayView<T>>();
 
     c
         /* Constructor */
@@ -603,8 +600,6 @@ Containers::Pair<py::object(*)(const char*), void(*)(char*, py::handle)> accesso
 template<unsigned dimensions, class T> void stridedArrayView(py::class_<Containers::PyStridedArrayView<dimensions, T>, Containers::PyArrayViewHolder<Containers::PyStridedArrayView<dimensions, T>>>& c) {
     /* Implicitly convertible from a buffer */
     py::implicitly_convertible<py::buffer, Containers::PyStridedArrayView<dimensions, T>>();
-    /* This is needed for implicit conversion from np.array */
-    py::implicitly_convertible<py::array, Containers::PyStridedArrayView<dimensions, T>>();
 
     c
         /* Constructor */

src/python/magnum/magnum.cpp

@@ -90,40 +90,19 @@ template<class T> void imageView(py::class_<T, PyImageViewHolder<T>>& c) {
     py::implicitly_convertible<Image<T::Dimensions>, T>();
 
     c
-        /* Constructors. The variants *not* taking an array view have to be
-           first, otherwise things fail on systems that don't have numpy
-           installed:
-
-            ===================================================================
-            ERROR: test_init_empty (test.test.ImageView)
-            -------------------------------------------------------------------
-            Traceback (most recent call last):
-              File ".../magnum/test/test.py", line 102, in test_init_empty
-                b = ImageView2D(storage, PixelFormat.R32F, (8, 8))
-            ModuleNotFoundError: No module named 'numpy'
-
-           This is because of the order in which pybind processes arguments ---
-           it would first try to match the (PixelFormat, Vector2i, ArrayView)
-           variant and *somehow* getting all the way to the third argument,
-           where, because ArrayView is marked as implicitly convertible from
-           py::array for numpy compatibility, it ends up doing this in numpy.h:
-
-            module m = module::import("numpy.core.multiarray");
-            auto c = m.attr("_ARRAY_API");
-
-           Wonderful, isn't it. */
-        .def(py::init([](const PixelStorage& storage, PixelFormat format, const typename PyDimensionTraits<T::Dimensions, Int>::VectorType& size) {
-            return T{storage, format, size};
-        }), "Construct an empty view")
-        .def(py::init([](PixelFormat format, const typename PyDimensionTraits<T::Dimensions, Int>::VectorType& size) {
-            return T{format, size};
-        }), "Construct an empty view")
+        /* Constructors */
         .def(py::init([](const PixelStorage& storage, PixelFormat format, const typename PyDimensionTraits<T::Dimensions, Int>::VectorType& size, const Containers::ArrayView<typename T::Type>& data) {
             return pyImageViewHolder(T{storage, format, size, data}, pyObjectHolderFor<Containers::PyArrayViewHolder>(data).owner);
         }), "Constructor")
         .def(py::init([](PixelFormat format, const typename PyDimensionTraits<T::Dimensions, Int>::VectorType& size, const Containers::ArrayView<typename T::Type>& data) {
             return pyImageViewHolder(T{format, size, data}, pyObjectHolderFor<Containers::PyArrayViewHolder>(data).owner);
         }), "Constructor")
+        .def(py::init([](const PixelStorage& storage, PixelFormat format, const typename PyDimensionTraits<T::Dimensions, Int>::VectorType& size) {
+            return T{storage, format, size};
+        }), "Construct an empty view")
+        .def(py::init([](PixelFormat format, const typename PyDimensionTraits<T::Dimensions, Int>::VectorType& size) {
+            return T{format, size};
+        }), "Construct an empty view")
         .def(py::init([](Image<T::Dimensions>& image) {
             return pyImageViewHolder(T{image}, image.data() ? py::cast(image) : py::none{});
         }), "Construct a view on an image")