[bug] `required_conan_version` is not evaluated before python imports

Environment Details (include every applicable attribute)

• Operating System+version: macOS Monterey
• Compiler+version: apple-clang 13.1
• Conan version: 1.48.0
• Python version: 3.9.12

Steps to reproduce (Include if Applicable)

see https://github.com/conan-io/conan-center-index/pull/10633#issuecomment-1124783149

• use conan < 1.45.0, for example 1.44.0
• conan install yaml-cpp/0.6.3
• Instead of the meaningful message ERROR: Error loading conanfile at (...): Current Conan version (1.44.0) does not satisfy the defined one (>=1.45.0). we could expect due to required_conan_version = ">=1.45.0", there are python imports error.

Logs (Executed commands with output) (Include/Attach if Applicable)

log from https://github.com/conan-io/conan-center-index/pull/10633#issuecomment-1124783149:

00:00:22  yaml-cpp/0.6.3: Retrieving from server 'conancenter'
00:00:22  yaml-cpp/0.6.3: Trying with 'conancenter'...
00:00:22  Downloading conanmanifest.txt
00:00:22  Downloading conanfile.py
00:00:22  Downloading conan_export.tgz
00:00:22  yaml-cpp/0.6.3: Downloaded recipe revision 0
00:00:22  ERROR: yaml-cpp/0.6.3: Cannot load recipe.
00:00:22  Error loading conanfile at '***/CONAN_CACHE_arm64/.conan/data/yaml-cpp/0.6.3/_/_/export/conanfile.py': Unable to load conanfile in ***/CONAN_CACHE_arm64/.conan/data/yaml-cpp/0.6.3/_/_/export/conanfile.py
00:00:22    File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/imp.py", line 171, in load_source
00:00:22      module = _load(spec)
00:00:22    File "<frozen importlib._bootstrap>", line 711, in _load
00:00:22    File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
00:00:22    File "<frozen importlib._bootstrap_external>", line 850, in exec_module
00:00:22    File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
00:00:22    File "***/CONAN_CACHE_arm64/.conan/data/yaml-cpp/0.6.3/_/_/export/conanfile.py", line 1, in <module>
00:00:22      from conan.tools.microsoft import is_msvc, is_msvc_static_runtime
00:00:22  ImportError: cannot import name 'is_msvc' from 'conan.tools.microsoft' (***/lib/python3.9/site-packages/conan/tools/microsoft/__init__.py)

[memsharded]

https://github.com/conan-io/conan/pull/11908 merged, this will be in 1.52

[memsharded]

I was thinking about trying to locate the required_conan_version “manually” only after getting an ImportError (to improve the error message if we locate the required_conan_version, or keep raising otherwise)

Oh, that could be a better approach, indeed. We could give that a try 👍