Use a more descriptive error message if love.graphics.newImage fails because the OpenGL texture can't be created.

src/modules/graphics/opengl/Image.cpp

@@ -356,7 +356,7 @@ bool Image::loadVolatile()
 
 		GLenum glerr = glGetError();
 		if (glerr != GL_NO_ERROR)
-			throw love::Exception("Cannot create image (error code 0x%x)", glerr);
+			throw love::Exception("Cannot create image (OpenGL error: %s)", OpenGL::errorString(glerr));
 	}
 	catch (love::Exception &)
 	{

src/modules/graphics/opengl/OpenGL.cpp

@@ -32,6 +32,7 @@
 
 // C
 #include <cstring>
+#include <cstdio>
 
 // For SDL_GL_GetProcAddress.
 #include <SDL_video.h>
@@ -652,6 +653,36 @@ OpenGL::Vendor OpenGL::getVendor() const
 	return vendor;
 }
 
+const char *OpenGL::errorString(GLenum errorcode)
+{
+	switch (errorcode)
+	{
+	case GL_NO_ERROR:
+		return "no error";
+	case GL_INVALID_ENUM:
+		return "invalid enum";
+	case GL_INVALID_VALUE:
+		return "invalid value";
+	case GL_INVALID_OPERATION:
+		return "invalid operation";
+	case GL_OUT_OF_MEMORY:
+		return "out of memory";
+	case GL_INVALID_FRAMEBUFFER_OPERATION:
+		return "invalid framebuffer operation";
+	case GL_CONTEXT_LOST:
+		return "OpenGL context has been lost";
+	default:
+		break;
+	}
+
+	static char text[64] = {};
+
+	memset(text, 0, sizeof(text));
+	sprintf(text, "0x%x", errorcode);
+
+	return text;
+}
+
 const char *OpenGL::debugSeverityString(GLenum severity)
 {
 	switch (severity)

src/modules/graphics/opengl/OpenGL.h

@@ -339,6 +339,8 @@ public:
 	 **/
 	Vendor getVendor() const;
 
+	static const char *errorString(GLenum errorcode);
+
 	// Get human-readable strings for debug info.
 	static const char *debugSeverityString(GLenum severity);
 	static const char *debugSourceString(GLenum source);