AttributeError: 'NoneType' object has no attribute 'f_locals'

**Affects:** PythonCall

**Describe the bug**
Minimal working example:

```julia
using PythonCall

sym = pyimport("sympy")

a = sym.Symbol("a", positive=true)
sym.lambdify(a, a)
```

```julia
Python: AttributeError: 'NoneType' object has no attribute 'f_locals'

Stacktrace:
[1] pythrow()
@ PythonCall.Core [~/.julia/packages/PythonCall/bb3ax/src/Core/err.jl:92](https://file+.vscode-resource.vscode-cdn.net/home/alberto/GitHub/PhD-Thesis-Notebooks/~/.julia/packages/PythonCall/bb3ax/src/Core/err.jl:92)
[2] errcheck
@ [~/.julia/packages/PythonCall/bb3ax/src/Core/err.jl:10](https://file+.vscode-resource.vscode-cdn.net/home/alberto/GitHub/PhD-Thesis-Notebooks/~/.julia/packages/PythonCall/bb3ax/src/Core/err.jl:10) [inlined]
[3] pycallargs(f::Py, args::Py)
@ PythonCall.Core [~/.julia/packages/PythonCall/bb3ax/src/Core/builtins.jl:212](https://file+.vscode-resource.vscode-cdn.net/home/alberto/GitHub/PhD-Thesis-Notebooks/~/.julia/packages/PythonCall/bb3ax/src/Core/builtins.jl:212)
[4] pycall(::Py, ::Py, ::Vararg{Py}; kwargs::@Kwargs{})
@ PythonCall.Core [~/.julia/packages/PythonCall/bb3ax/src/Core/builtins.jl:230](https://file+.vscode-resource.vscode-cdn.net/home/alberto/GitHub/PhD-Thesis-Notebooks/~/.julia/packages/PythonCall/bb3ax/src/Core/builtins.jl:230)
[5] pycall(::Py, ::Py, ::Vararg{Py})
@ PythonCall.Core [~/.julia/packages/PythonCall/bb3ax/src/Core/builtins.jl:220](https://file+.vscode-resource.vscode-cdn.net/home/alberto/GitHub/PhD-Thesis-Notebooks/~/.julia/packages/PythonCall/bb3ax/src/Core/builtins.jl:220)
[6] (::Py)(::Py, ::Vararg{Py}; kwargs::@Kwargs{})
@ PythonCall.Core [~/.julia/packages/PythonCall/bb3ax/src/Core/Py.jl:339](https://file+.vscode-resource.vscode-cdn.net/home/alberto/GitHub/PhD-Thesis-Notebooks/~/.julia/packages/PythonCall/bb3ax/src/Core/Py.jl:339)
[7] top-level scope
@ In[8]:5
```

**Your system**

```julia
Status `~/GitHub/PhD-Thesis-Notebooks/Project.toml`
[992eb4ea] CondaPkg v0.2.22
[429524aa] Optim v1.9.4
[6099a3de] PythonCall v0.9.19
[6c2fb7c5] QuantumToolbox v0.7.2
[a25cea48] SpecialPolynomials v0.4.9
```

```julia
julia> versioninfo()
Julia Version 1.10.2
Commit bd47eca2c8a (2024-03-01 10:14 UTC)
Build Info:
Official https://julialang.org/ release
Platform Info:
OS: Linux (x86_64-linux-gnu)
CPU: 32 × 13th Gen Intel(R) Core(TM) i9-13900KF
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-15.0.7 (ORCJIT, goldmont)
Threads: 32 default, 0 interactive, 16 GC (on 32 virtual cores)
Environment:
JULIA_EDITOR = code
JULIA_NUM_THREADS = 32
```

```julia
CondaPkg Status /home/alberto/GitHub/PhD-Thesis-Notebooks/CondaPkg.toml
Environment
/home/alberto/GitHub/PhD-Thesis-Notebooks/.CondaPkg/env
Packages
numpy v1.26.4
sympy v1.12
```

**Additional context**
Add any other context about the problem here.